The

Handloader Magazine

U.S. & Canada, $1.00

auto pistol loading 1

Handloader j n e Magazine

DAVE WOLFE Publisher

NEAL KNOX Editor

ROGER T. WOLFE, Ph.D. Associate Editor

JAMES D. CARMICHEL Associate Editor

NORM LAMMERS Technical Adviser

HOMER POWLEY Ballistics Adviser

MAJ. GEORGE C. NONTE JR. General Assignment

PARKER 0. ACKLEY Wildcats & Gunsmithing

WALLACE LABISKY Sho tshells

JOHN WOOTTERS Gun Tests

HARVEY A. DONALDSON Historical Adviser

KEN WATERS "Pet Loads"

EDWARD M. YARD General Assignment

DON ZUTZ General Assignment

BOB HAGEL Hunting Adviser

JOHN BUHMILLER African Cartridges

DAVE LeGATE Production

BARBARA LAFFEY Circulation Manager

JANE CLARK Asst. Circulation Mgr.

POLLY STARBUCK Editorial Assistant

ROY STARBUCK Promotion

Mar.-Apr., 1971 Vol. 6-No. 2 Box 3030, Prescott, Ariz. 86301

Features:

Handloading for Auto Pistols . . . . . . . Maj. George Nonte Shotgun Chronographing. . . . . . . . . . . . DonZutz

.44 T/C Contender Shotshells . . . . . . . Wallace Labisky

.444 Marlin . . . . . . . . . . . . . . . . . Ken Waters

.224 Varmint Bullet Accuracy. . . . . . . . . . Bob Hagel

New AA .410 Components . . . . . . . . Wallace Labisky Pressure Factors Part XI I I . . . . . . Lloyd Brownell, Ph.D.

Reviewing the Basics: Creative Handloading. . John Wootters

14 18 20 22 26 30 34 38

Departments:

Reader Bylines. . . . . . 5 Answers Please. . . . . . 12 Editorial . . . . . . . . 6 Propellant Profiles . . . . 25 Lock, Stock and Barrel. . . 8 Cartridge of the Month. . . 37 Tip to Tip. . . . . . . . 10 ProducTests. . . . . . . 62

Harvey Donaldson . . . . 66

The H A N D L O A D E R . Copyright 1971, i s published b i -month ly b y the Dave Wolfe Publishing Company, P.O. Box 3030, Prescott, Arizona 86301. (Also publisher o f Rif le Magazine.) Telephone (602) 445-7810. Second Class Postage paid at Prescott, Arizona, and addit ional mail ing offices. Single copy price o f current issue $1.00. Subscript ion price: six issues $5.00; 1 2 issues $9.00; 1 8 issues $12.50. Outside U.S. possessions and Canada $6.00, $11.00 and $15.50. Recommended foreign single copy price, $1.25. Advert ising rates furnished o n request.

Publisher o f The H A N D L O A D E R I S n o t responsible for mishaps o f ~SHOOTING~ - --- any nature which might occur f r o m use o f published loading data, o r f r o m recommendations by any member of The Staff. N o part o f this Dubllcation may be reDroduced w i thou t wr i t ten permission f r o m the editor. Manuscripts f r o m free-lance writers must be accompanied by stamped self-addressed envelope and the publisher cannot accept responsibi l i ty for lost or mut i la ted manuscripts.

Change of address. Please give one month's notice. Send bo th o l d and new address, plus mail ing label i f possible. t o Circulat ion Dept.. The H A N D L O A D E R Magazine. P.O. Box 3030, Prescott, Arizona 86301

Official Publication o f Santa Barbara Reloading Association

Your March-April Cover

Plastic and paper shotshell hulls blend into a rainbow o f colors on this month? cover. You readers who have attended either the NSGA or N R A conventions over the past four years wil l recognize this photo, for a greatly enlarged version is featured in the Wolfe Publishing

Co. exhibit. Transparency by Walter Schwarz o f Peoria, Illinois.

4 HANDLOADER - March-April. 1971

PRESSURE By Lloyd Bro wnell, Ph. 0. Part XIII:

ASE VOLUME is the last of C t h e p ressure factors to be

considered in this series of articles and is one of the most important. Case volume, powder quickness, powder charge weight, and caliber are the four most influential pressure factors of internal ballistics. This is demonstrated in this final article by a General Equation applicable to all high-pressure, centerfve cartridges for all calibers, all case shapes and all case volumes. A number of other factors such as the bore and groove diameters of the barrel, microdiameter of the bullet, case diameter, case length, case shoulder angle, powder orientation in the case and primer characteristics are recognized as having an influence on chamber pressure, but are not scheduled for analysis in this series. However, the influence of case diameter, length and shoulder angle is expressed as case factor “0.” Examples of the use of 0 including equations for computation for one powder, IMR 4227, are given in this article.

The factors treated in the earlier articles have included the usual options open to the handloader, such as the choice of bullet weight and powder type. The selection of the powder type fixes an important factor for the handloader, the relative quickness q(test) determined from firing data. The procedure for use of relative quickness as measured in a rifle is new to most handloaders and has been used to date by only a few. The new method offers the handloader much in that it gives a means of analysis of the combined effect of all variables that influence the burning rate of the powder in the rifle. One difficulty in the use of relative quickness is related to its definition. Originally, relative quickness based on rifle test data was defined as the ratio of the charge weight of a reference powder such as IMR No. 3031 to the

38

charge weight of the powder being tested that produces the same reference pressure (50,000 psic) using the same components and loading conditions.

Most handloaders d o not have access to apparatus for measuring chamber pressures which prevents determination of the relative quickness by this technique. Fortunately for those who may be interested in the usefulness of relative quickness for analysis of rifle, bullet and powder characteristics, there has been a recent break-through in this measurement. Oscar Carlson, engineer, handloader and a helpful critic of my articles in The Handloader Magazine has found a new procedure for determination of relative quickness from velocity measurements. Carlson determines “q(ve1)” from the ratio of charge weights of powders that produce equal muzzle velocities when using the same loading conditions except for powder and powder charge weight. This ratio is raised to the 312 power as shown below:

Relative Quickness of Powder X Based on Equal Velocity

Where: L (3031)

L (Powder X)

L (Powder X : [I = (3031) r

Charge weight of IMR No. 3031 powder to give any selected muzzle velocity “v” and a corresponding but undetermined pressure in the high to normal range (40,000 to 60,000 psic). Charge weight of powder X to give the identical selected velocity “v” and a corresponding un- determined pressure in the same range.

vel) = Relative quickness of powder X based on the charge weight ratio to give identical velocities using the same components of bullet, rifle barrel, cartridge case, primer, seating depth, but different powders and different powder charge weights.

q(ve1) s q(test)

Larlson has found the Hornady Handbook of Cartridge Reloading convenient for computation of q(ve1) because it lists the charge weights for different powders that give the same velocities using the same bullet weights and the same cartridges. An excerpt from his letter of September 22, 1970, and his Table A illustrate a comparison of relative quickness values computed by the two procedures for the 100-grain bullet in the .257 Roberts cartridge. Carlson points out that the Du Pont data for this load using IMR No. 4320 powder appear inconsistent, possibly

U K I V H U ,900 fps I

HANDLOADER - March-Aprll, 1971

FAC T OR S 1

1

because of the use of a different barrel for this firing. With this exception his computations demonstrate the general good agreement of the two relative quicknesses, q(test) and q(ve1). Carlson comments:

“I have done some more correlating and find this (the q(ve1) relationship) a very handy tool; for example, I have been using a .25-06 and correlated data to and with the ,257 Roberts data. So . , . I don’t agree with the Du Pont .257 Roberts data, nor data on same in Table 21. The Hornady data follow the 3 /2 power formula . . . it appears that Du Pont conditions differed from the Hornady data conditions which follow the normal expected values of relative speed.

“You will note (in Table A) from the velocity per grain that Du Pont showed excessively high results with the 4320 compared to those for Hornady. This may have been tied to the effect of using a pressure barrel, or maybe two different barrels were used for the tests; whatever, I find no correlation for the speed of 4320 over its otherwise nominal value.”

Table A lists the values of relative quickness as computed by Carlson in the right hand column. As he points out, the value of q(test) of .96 for IMR 4320 powder is high compared to the value of .91 for q(ve1) based on the Hornady data and also is high based on most of the other values of q(test) for IMR 4320 that hold close to .91 for this powder.

My opinion is that Carhon has disclosed another uninvestigated Subsystem (see brackets in Table 21) that appears to relate the value of q(test) for IMR 4320 to the value of “W”, the combined resistance of the

HANDLOADER - March-April, 1971

barrel and bullet. The .257 Roberts used in the Du Pont tests apparently barrel used in the Du Pont tests was similar in that it also gave a high apparently was very “tight” as the value of q(test) for IMR 4320 of .96

is 2.05. The 6mm Remington barrel comparison the 244 Remington barrel computed W based on IMR 4227 data and a computed W of 2.10.

0.1 1.0 lo?*?-- I 8.0 -.. I 1 I I I I l l - 6.0 -

L

4.0 - 3.0 -

\o 0.8 I 0

L

r( 0.6 - w

- v)

Om4 - Ec - . 0.3 m v\

Om2 - E5 H E.l 4

w ~ 0.08 0

Y

Om10 - - = Om06 - - - : Omo4 B 0.02

Om03 c - I e22 Hornet--\ b-bcm-

-3.0

- 2 .0

- le0 - Om8 - - - 0.6 - - Om4

0.3

0.2

- -

- Om10 - - 0.08 - - 0.06 - - 0.04 - Om03 - Om02

I I I $ 1 I I l l I I I I l l l l l o m o l m4 e 6 1.0 .04 .06 0.1 a2

CASE VOLUME, V, Cubic Inches

Om01 e 0 1 e 0 2

FIG. 62-Constant ’k“ as a Function of Case Volume, V For All Cartridges (See Equation 53).

39

used in the Du Pont tests gave a low value of q(test) of only .88 for IMR 4320 and a value of W of 1.30. Thus the high value of .96 for q(test) for the Du Pont ,257 Roberts is believed to be the result of a “tight” barrel rather than possibly a quicker lot of powder. The Hornady barrel apparently gave normal resistance.

The question remains as to whether or not q(ve1) for IMR 4320 will also show a difference between a “tight” and a “loose” barrel. Although the numerical values may be similar as shown by Carlson, q(test) and q(ve1) have basic differences. The value of q(test) is determined by the powder burned over the distance the bullet travels to reach the peak pressure, whereas q(ve1) is determined by the powder burned during bullet travel over the entire barrel length. Thus the two relative quicknesses may be as different as a mulie and a white tail, both being deer but with different characteristics. Carlson’s study of q(ve1) may answer some of these questions and does point up the analytical value of chronographing loads.

Now, before we close this series on Pressure Factors, a brief resume is appropriate for the benefit of readers who may have missed some of the earlier issues of The Handloader. Also this resume is necessary to show why certain corrections must be introduced

in the final correlation. The first two articles of this series considered the influence of the weight (or mass) m of the bullet and the charge weight (or load) L of powder. The force to produce a given acceleration of a bullet of given mass is directly proportional to the mass. The result is a linear relationship between pressure p and bullet mass m. This relationship based on bullet mass alone is an approximation because a portion of the mass of powder gas also is accelerated with the bullet. A better correlation is obtained if a refinement is introduced that corrects for the acceleration of the powder gas. The correction has been given considerable attention in classical ballistics and was studied by the French mathematician Lagrange. The procedure used in Systems Ballistics is different and involves the introduction of the dimensionless ratio L/m raised to the 1/3 power as demonstrated in Part 12.

Some additional comments also need to be made regarding the exponent of 4 used to predict the pressure influence of the powder charge weight L. Fig. 6 in the first article of this series shows data on the influence of powder charge weight L on the maximum chamber pressure p for the .30-06 cartridge and a 220-grain bullet. The pressure varies in a nearly linear manner with the charge weight up to about 20,000 psi based on mean values and neglecting the scatter of the data. This means that

in the pressure range of O to 20,000 psi, the exponent on L is 1.0 and as indicated in Fig. 6 a charge weight of 10 grains of IMR 3031 powder would be expected to produce a pressure of about 10,OOO psi and a charge of 20 grains, a pressure of about 20,000 psi. But in the pressure range of 20,000 to 35,000 psi the curve in Fig. 6 bends upward and the exponent on the charge weight increases rapidly from 1.0 to 4.

Considerable scatter of the data occur in this pressure range and this region has been avoided as far as possible in the Systems Ballistics correlations. However, this is the pressure range for the rifles used at the turn of the century and for the older designs of artillery pieces. Because of this many of the earlier ballistic equations such as those developed by Le Duc and by C. A. Clemmow (author of A Pressure- Index Law of Burning Propellants) have constants selected to fit this range of pressures. The equivalent exponents on powder charge weight as determined from these equations usually are in the range of 2 t o 3. As a result these older equations usually do not give as satisfactory solutions in the pressure range of about 50,000 psi crusher value used for modern rifles as they do in the lower pressure range used 50 or more years ago.

There also is another reason for the higher exponent of 4.0 and this relates

HANDLOADER - March-April, 1971 40

to the use of true or “absolute” pressures rather than crusher gauge values. Crusher gauges were first used about a century ago to measure chamber pressures. They have proven very useful and are still used. They have the advantage of simplicity but a disadvantage of being nonlinear with pressure in the range of interest of 40,000 t o 60,000 psi crusher values. They give lower readings than electronic gauges that are linear with pressure over the complete pressure range. Most of the pressure data reported by the firearms industry and by the NRA has been in terms of crusher values. An approximate relationship between crusher gauge values and true or “absolute” pressure as measured by electronic gauges that are linear was shown in Fig. 8 of the first article. If the crusher gauge values are converted to absolute pressures and plotted as shown in Fig. 7, the absolute pressure varies as the 4th power of the charge weight of powder in the pressure range from about 40,000 to 100,000 psia.

The use of the absolute pressure raises the numerical value of the pressure term which has the effect of raising the exponent (or the pressure index) on the powder charge weight term L to 4.0. Accordingly, a lower exponent or a correction factor must be used if crusher values are used in the equations relating the powder charge weight to pressure.

In this series new procedures have been introduced for the first time to characterize individual bullets and individual rifle barrels in regard to their influence on pressure. The new procedure involves the definition of a bullet jacket factor J and a rifle barrel factor R that describe the individual characteristics of each of these two components in regard to pressure. The bullet and the barrel are mating components and their influence on pressure combine as their product, J times R. These new factors were first introduced as gross values in the third article, Jacket Factor, and the fourth article, Rifle Barrel Factor. The next three articles were used to refine these concepts and to show the relationship of J and R to other factors such as seating depth of the bullet, the bullet travel distance before engagement of the rifling (termed the freebore travel), and the apparent relative quickness of the propellant powder. These factors influence the overall values of J times R, the combined resistance of the bullet and the barrel producing wide ranges HANDLOADER - March-April. 1971

in the apparent values of J and R. These ranges are shown to result in part from the influences of a Seating Depth Factor S and a Freebore Travel Factor F described in the sixth and seventh articles respectively. Use of these two new factors S and F permitted a redefinition of the overall influence of the bullet-barrel-seating depth-freebore travel combination as equal to J times R’ times S times F, with the total product termed “W”, or by Equation (56):

w= J OR’ O S 0 F

Where: W= The combined effective factor for bullet, barrel, seating depth, and freebore factors.

d= The rifle barrel factor normalized to a crusher value of 50,000 psi, a seating depth of s = n, and a freebore travel of 1.80 calibers.

The evaluation of W is one of the keys to a better understanding of the bullet-barrel-seating-freebore interrela- tionship and how it influences pressure. Also, the evaluation of W and its components will prove useful in determination of the optimum use of freebore and seating depth and will aid in the evaluation of improvements in bullet characteristics and improvements in rifle barrel chambering.

All of the factors described so far in this article can be studied using a single caliber, in fact only a single type of cartridge, such as the .30-06 used in the tests conducted at the University of Michigan during the Du Pont Grant studies. To permit the analysis of other cartridges, the influence of caliber was introduced into Equation (53) as the fourth power of d, the major diameter of the bullet as described in the last previous article “Caliber.” This was done by analysis of the influence of d on the constant “k” of Equation (53) for cartridges with same case shape and same case volume. This analysis is continued in this final article using the same technique and including the caliber correction given by Equation (53) but changing case volume. The results show that the pressure varies inversely as the cube of the case volume V for cartridges with the same shape but different case volumes.

Case shape also is involved but can be treated only briefly. Case shape is defined by a number of case dimensions

such as: the case shoulder angle “a” measured from the longitudinal axis of the case, the mean diameter of case between the case base and the case shoulder, and the case length from the head to the juncture of the neck and the case shoulder. The influence of these dimensions on the maximum chamber pressure is compared to that for a reference cartridge, the -30-06, and the ratio of the net effect defined as “O”, the overall influence of case shape on pressure for a particular powder. These two factors of case volume “V” and case shape factor “0” complete the variables necessary to write the General Equation that applies to all cartridges.

Figure 62 is a plot of the General Equation and shows data points for 34 different cartridges from the .22 Hornet to the .458 Winchester Magnum and .375 H&H Magnum. The plot is of the logarithm of constant “k” as a function of the logarithm of the case volume “V.” The slope of the line is 6 cm/ 18 cm or 3.0. The intercept at V = 0.1 is k = 0.091 x 106 or k = 91 x 106 at at V = 1.0. Therefore the line drawn through the data points in Fig. 6 2 can be described by Equation (57) as follows:

k =

k = 91(100V)3

91 x lo6 x V3 or:

Equation (57) is substituted f o r k in Equation (53) given in the previous article on “Caliber” to give the General Equation (58) that applies to all cartridges as follows:

m

p = ( C ) 9 1 ( 1 0 0 V )

For convenience in computation the numerator and the denominator in the equation above are each multiplied by 1OOV and the terms are collected and rearranged as below:

Where:

p= The crusher value of the maximum chamber pressure in psi as reported in Du Pont’s Handloader’s Guide to Powders or 1968-69 or in the NRA’s HandloaLr’s Guide and other references giving maximum chamber pressures in crusher gauge values.

41

C=

Table

The conversion factor t o , convert crusher values to “absolute” or true pressure as indicated by the curve in Fig. 8 of the first article “Powder Load.” The value of “c” is equal to the ratio of the absolute pressure divided by the corresponding crusher value and varies with the crusher value approximately as shown below:

B - Crusher Correction Factor “c” Versus Pressure

Crusher psi ‘‘C” Absolute psi 30,000 1.05 31,500 35,000 1.09 38,150 40,000 1.13 45,200 45,000 1.18 53,100 50,000 1.23 61,500 55,000 1.29 72,000

W = Combined influence of bullet, barrel seating and freebore travel on pressure, dimensionless. See Eq. (56).

Combined influence of case shape on pressure, dimensionless, and a specific constant for a given powder and given case.

0 =

O(4227) =

Where:

A =

B =

C =

a =

D =

b =

m =

V =

q =

9 =

L =

d =

j 2 ForIMR 4227 powder and all cases Equation (59)

;I - Case shoulder factor (4227) Equation (60)

Case diameter factor (4227) Equation (61)

[ - + q= Casesize factor (4227)

Angle of case shoulder with longitudinal axis.

Averagediameter ofcasebetween case base and case shoulder, 0. D. inches.

Length of case from base to junction of the shoulder with neck, inches.

Mass (weight) of bullet, grains.

Volume of case for a fired cartridge measured to the junc- tion of the shoulder with neck, (Same as Vo in Part 6 ) cubic inches,

Normal relative quickness of powder as compared to a ref- erence ( IMR 3031) powder, dimensionless.

[q+d Equation (62)

l 3 For IMR 4227 Equation (52)

Charge weight (load) of powder, grains.

Diameter ( major ) of bullet, inches.

Writing the General Equation in the form shown by Equation (58) helps to demonstrate the nature of the relation-

42

ship. On the left side of the equation we have the term “plow.” This is the crusher pressure “p” divided by the influence of the case shape factor “0” and the bullet-barrel effective (or com- bined) factor “W.” These are the quantities that are determined from the results of firing tests such as Du Pont’s for the cartridge, powder, and other compcnents of interest. The relative “q” is not included in this group because it and the other variables on the right side of the equation must be known from other considerations. For instance, the normal relative quickness for IMR 4227 powder is given by Equation (52) above. Usually this value of q(4227) is not quite equal t o the specific value of q(4227) for a particular cartridge, barrel, bullet, seating depth combination as listed in Tables 17, 19 and 21.

The difference between the expected or normal value of q(4227) as given by Equation (52) and the specific values of q(4227) as listed in these tables is considered to be the result of the individual characteristics of specific com- bination of bullet, barrel, seating depth and cartridge shape used. This difference is equal to the product of “0” times “W”. The procedures for determination of the values of W from the normal relative quickness were introduced in Part 11- “Systems Ballistics” and are considered in some detail for both W and O in two unpublished articles considered too technical for the majority of Handloader readers and are not included in the series. These explained necessary steps in the development of the formulas, but were not considered essential to their application.

As used in this last article the absolute pressure is defined simply as the crusher value “p” times a correction factor “c” or absolute pressure equals ‘‘pc,” and the value of the correction factor “c” varies with the pressure as shown in Table B. By this procedure we can have both a corrected pressure and yet retain the useful and familiar crusher values, In the instance of Equation (58) the expression becomes an equation in terms of absolute pressure if the crusher correction factor “c” is simply transposed from the right t o the left side of the equation to give “pc/OW” on the left with pc equal to the absolute pressure in psia.

The transposition of “c” as above only involves multiplication of both sides of the equation by c which

leaves the product “(1.1 V m)” as a multiplier t o the terms in brackets as the right. Some comment in regard to the significance of the terms in this product is appropriate. The number “1.1” might be considered to be a “general” constant of the General Equation and is the same for all cartridges, all calibers, all powders and all other components. In Part I: “Powder Load” a beginning was made with the very simple equation of p = a Lo with “a” being a very specific constant for a specific cartridge, a specific weight of bullet, and in fact a specific rifle barrel, specific type of bullet and specific seating depth. In the interim series of articles all these specifics have been removed by evaluation of the individual factors in the General Equation thereby reducing the highly specific constant “a” first to more general constants k , , k,, etc., then to k, as used in Equation (57) and finally to completely nonspecific 1.1.

The case volume V appears as a multiplier in the product (1.1 V m) purely as a correction term. The peak pressure varies inversely as the cube of the case volume or as 1/V3 as shown in Fig. 62 and in Equation (57). This is the result of the combined influence of case volume on the initial rate of pressure rise and therefore on the initial burning rate plus the influence on the available volume at the peak pressure as developed in the previous article on “Caliber.” However, the loading density, the term used for the weight of powder charge per unit of case volume, or LIV, has been shown by many ballisticians to be a very useful ratio in the interpretation of firing data. To use loading density, L/V in the General Equation, the most simple procedure is t o multiply the numerator and the denominator of the fraction of 1/V3 by V to give V/V4 which does not change the value of the fraction. This permits the inclusion of V4 in the denominator inside the brackets of the terms raised to the 4th power but leaves V as a correction to this step and as a multiplier in the product (1.1 V m).

The term “m” in the product (1.1 V m) is an anticipated multiplier because it represents bullet mass. The force required for a given acceleration is linearly proportional t o the mass accelerated. As mentioned previously the use of the bullet mass alone for the mass accelerated is an approximation

WANDLOADER - March-April. 1971

because some of the powder gas is accelerated with the bullet. The theory involved in the correction for the acceleration of the powder gas is quite complex. The correction is related to L/m, the ratio of the charge weight L to the bullet weight m. For simplicity an empirical correction based on this ratio of L/m and on test firing data was used. The correction in main part is made by using the cube root of this ratio of (L/m)1/3 and in part also involves the numerical value of 1.1. The net influence of this correction to the mass accelerated was determined from test firing data and may be considered to involve the combined product of 1.1 m (L/m)’/3.

The remaining terms of Equation (58) that are within the brackets and raised to the 4th power give the “core” number. The four terms and the number IO0 for convenience can be treated as the product of two ratios. These ratios are first, the relative quickness q divided by d the caliber in inches or q/d; and second, the powder charge weight L in grains divided by 100 V, the case volume in cubic inches times 100 giving L/lOOV. Both of the ratios qld and L/1OOV usually have numerical values in the range of 1.0 to 6.0 which simplifies mental arithmetic and manual computations of multiplication and raising to power 4 without losing track of the decimal point. For example, with the .30-06 cartridge, a 220-grain bullet, a case volume of 0.242 cubic inches, a charge of 26.5 grains of IMR 4227 powder is used with a relative quickness of 1.54: determine the core number. In this example the ratio qld equals 1.5410.308 or 5.00. This value of 5.00 is constant for all .30 caliber cartridges and IMR4227 powder. The value of the ratio L/lOOV equals 26.5124.2 or 1.095. The product of q/d times L/lOOV is 5.475 which raised to the 4th power is 898 for the core number by slide rule computation.

To complete an example computation of the crusher pressure developed by the .30-06 load described above, some additional data are required. These include information on case shape to permit computation of the case shape factor “O”. The cartridge dimensions can be obtained from Cartridges of the WorZd by Frank C. Barnes or from some of the handloading handbooks. For the .30-06 the chamber length “b” is 2.111 inches, the shoulder angle “a” is 17.3 degrees, and the mean outside diameter “D” is 0.455 inches.

HANDLOADER - March-April. 1971

Case shoulder factor “A” equals (17.3 - 3)/.455 or 45.1. Case diameter factor “B” equals (2.111 - 1.0)/(.455)2 plus 1.0 or 6.36. Case size factor “C” equals 5(.242)/2.111 plus 1.0 or 1.57. The overall shape factor “0” is equal to the square root of (45.1)(6.36)/(183) (1.57) or 1.00. The value of 1.00 for 0 for the .30-06 cartridge is to be expected because this cartridge has been used as a reference.

However, the value of W is never 1.00 and must be determined for each bullet, barrel, seating depth combina- tion. From Table 22 of Part 11 : “System Ballistics,” the following values were determined for this combination: J equals 1.38; R’ equals 1.00, S equals 1.04, F equals 1.60. Therefore W equals the product of (1.38)(1.00)(1.04) (1.60) or 2.30. These values and the value of 1.24 for “c” at 50,600 psi crusher provide sufficient information to compute the pressure by the General Equation. For this purpose it is convenient to rearrange the General Equation as Equation (63) below, and to use Equations (64), (65) and (66).

Winchester with a high of 126.5 for the .375 H&H Magnum. This is consistent with the fact that x is influenced primarily by the product of bullet weight m and case volume V and to a lesser extent by case shape factor 0. The value of y equal to (L/m)’ I3 is rather constant, remaining close to about 0.65. It drops to a low of 0.434 for the heavy 500-grain bullet used in the .458 Winchester load and rises to a maximum of 0.77 for the relatively high powder to bullet weight ratio used for the ,220 Swift load. With most cartridges and with more normal weight ratios this correction is not of major importance.

The sensitive core of the General Equation is the quantity “z” which varies from less than 1000 for the larger cartridges (778 for the .375 H&H Magnum) to several thousand for most of the smaller cartridges. If the case volume is less than 0.10 cubic inches, such as for the .357 Magnum and .22 Remington Fireball revolver cartridges or the .22 Hornet cartridge, the value of z may exceed 10,000. For the .22 Hornet cartridge the value of z rises 0

p = x y z ( 6 3 )

Where: I

p = Computed crusher value, psi

1.1 V m 0 W (64) X =

C

z = [-14

Substituting the values for the .30-06 into Equation (64) gives x as equal t o (1.1) (.242) (220) (1 .O) (2.30)/( 1.24) or 111.0. By Equation (65), y is equal to (26.5/220)1/3 or 0.494. By Equation (66) as previously shown, z equals (1.54 26.51.308 24.2)4 or 898. by Equation (63) the computed crusher value p equals (111.0)(0.494)(898) or 49,100 psi. This is about 3% lower than the value of 50,600 psi listed in the Du Pont tables.

Table 24 lists a summary of the computations for the .30-06 plus those for a variety of other cartridges with wide differences in case volume, case shape, caliber and bullet weight. Inspection of the table shows that product x varies from a low of 1.6 for the .22 Hornet, 9.05 for the .223 Remington, up to 105 for the .458

? lOST WABTED! P bv Outdoor Sportsmen I

BIGGEST VALUES! NAME BRANDS!

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43

to 38,000. The chief influence of case volunie V in the General Equation is in its effect on the core number z.

for this purpose. Muzzle velocity for a selected load is a function of the mean effective pressure and the barrel length. The value of W influences the peak

For the case of a selected load, an pressure and the mean effective pressure inspection of Equations (63) through and therefore it must also influence (66) shows that all the terms in “y” the muzzle velocity. This means that and “z’’ may be treated as constants W can be measured from velocity values for the selected loading conditions. This but probably with less sensitivity than means that if you pick a cartridge such from pressure values. The relationship as the .30-06, a 220-grain bullet and between velocity and W will be of a charge weight of 26.5 grains of IMR special interest to those handloaders 4227 powder as used in the previous who wish to analyze a particular rifle example, the values of y and z are barrel and bullet combination by fixed. This is true regardless of the measuring velocity rather than pressure. characteristics of the rifle barrel, the bullet type or manufacture, the seating Handloaders long have recognized depth or freebore travel. The influence that certain combinations of particular of these latter factors are found in bullets with specific barrels give better the product “x” and do not appear in accuracy than others. Also certain either y or z. bullet-barrel-powder combinations and

specific bullet-barrel-charge weight and Also, in product x most of the

terms such as 1.1, V, m and c are constants for a selected set of loading conditions. The case shape factor 0 which appears in x varies both with the cartridge shape and the type of powder but becomes a constant once these parameters are fixed. This leaves w as the only term that varies with pressure as different rifle barrels, different types of bullets (but with the same weight) and different seating depths are used. With the loading

specific bullet-barrel-seating depth com- binations are known to give better performance than others.

The identification of the values of w with the combinations that give measured degrees of performance is believed to be a step toward a better understanding of some of the factors leading to improved accuracy. A beginning in this direction would be made if authors of loading data would report the easily measured dimensions: -

conditions fixed, the numerical value s seating depth, e bullet engagement, of the pressure is directly proportional and f freebore travel distance. If these to the value of W for the bullet-barrel- dimensions were reported with pressute, seating depth combination used. Thus velocity, powder charge and bullet the influence of these components on identity the values of W could be more pressure can be used to define the easily determined for different bullet- individual characteristics of a particular barrel combinations. Development of barrel, a particular bullet or their com- procedures for the evaluation of W bined characteristics at a particular from velocity rather than pressure data seating depth. will permit handloaders to analyze their

own load combinations by the use of a chronograph. Carlson’s procedures for

that can be used to identify bullet and determination of quickness from barrel characteristics but is considered velocity values is a step in this direction. to be the most sensitive measurement

In closine I thank publisher Dave

Pressure is not the Only

” Wolfe and editor Neal Knox for the opportunity to present the new concepts described in this series. I thank the Du Pont Company for assistance in the early studies that kindled the interest in the new methods. I thank my former students who worked with me, especially Mike York, Warren Phillips and Tom Blackwood and also reader Oscar Carlson who have helped me in these studies and in presenting this series of articles. This has permitted me to open a door called Systems Ballistics that leads to a better understanding of the factors involved in handloading and ballistics. 0

Pet Loads -- .444 Marlin

(Continued from Page 24)

proved two things to the writer’s satisfaction:

(1) The most important point (with any rifle) is the location of brush in relation to the game. The longer the distance from intervening brush to the animal. the greater will be the likelihood of a miss due to deflection. If, on the other hand, the animal is standing no more than five or ten yards behind the screen, the chances of a good brush bullet getting through and hitting where its supposed to are greatly improved.

(2) Under such conditions we found the .444 doing very well indeed, even with factory ammunition. Deflection was quite negligible-far less than I would expect if using a high velocity smallbore; cut-off branches and saplings proved that our bullets were being interrupted.

I don’t say that heavier bullets with tougher jackets wouldn’t be even more sure of getting through. I’m just re- porting that the 240-grain bullets required no apologies.

Recoil, of course, is something to to be conjured with where any really powerful cartridge is concerned, whether the rifle fires a big heavy bullet at moderate velocity, or a 180-grain slug of lesser diameter at high velocity. To give you some idea of the amount of rearward push generated by the .444, my Marlin 336 rifle in this caliber, weighing 8-314 pounds complete with scope and mount, develops 23 fp of recoil with the factory cartridge. By comparison, a .30-06 rifle of equal weight firing a 180-grain full-power load churns up something like 16% fp of free recoil energy.

From these figures, i t should be apparent that while the “kick” of a .444 is substantial, it’s not going to produce any dislocated shoulders. The man used to firing an ’06 will experience no trouble in handling a .444, and if you have one of the .300 Magnums, I doubt that you’ll notice any appreciable difference a t all. The 1-5/8”x 4-718” recoil pad with which Marlin .444’s are factory-fitted plus a proper job of stocking, helps considerably in easing the jolt.

Accordingly, it appeared that the nucleus of our new investigation must

HANDLOADER - March-April, 1971 44

Weaver Classic Scopes

Last spring Weaver announced a new “Classic” line of fixed-power scopes in 3X, 4X and 6X. Actually, these new scopes do not depart greatly from the Weaver K series scopes as far as specs, but the Classics are lighter weight with aluminum alloy tubes. Tube diameter, field of view, eye relief and adjustment value per click are the same as on the K-models. The diameter of the eyepiece has been increased on the Classic to 1.500 from the 1.485 of the K line. The only change in objective bell size is in the 4X where the Classic measures 1.560 in diameter as opposed to 1.550 for the K4.

Length is the same on the 3X and 6X of both models, but the Classic 4X is 1/8-inch longer than the K4. Weight is perhaps where the largest change shows up externally; the new Classic line is 1%-2 ounces lighter than the same power in the K models, due to the latter’s steel tubes.

The finish on the Classic scopes is a shiny black, while that of the K scopes is a deep blue. The turret of the Classic is about %-inch longer than the K, and the dust caps are about 5/16-inch larger in diameter on the Classic. Also, the knurling on the dust caps and eyepiece lock ring has been changed from a series of grooves of equal width to four small grooves and a large one. This seems to give a somewhat better grip.

The adjusting knobs have undergone a change also, Where the K model had a knurled knob designed to be turned

62

New Weaver Classic 400, rop, compared to older Weaver K4.

with the fingers, and had the click mechanism on the outside of the dial, the Classic is coin slotted and the click mechanism i s internal. The dial turns inside an outer ring, and the inside has an arrow which points to silver lines on the outer ring, laid off in %, 1 and 3-minute increments.

The reason we are a little late in getting out this test writeup is due to the fact that the first pre-production batch of scopes had a few bugs which were later ironed out. This report is based on the production model, which came through very well in all respects.

The greatest change seemed to be in the improved optical quality of the new Classic 4X test scope as opposed to the K4. The K4 used as a comparison was some three years old and perhaps the ’70 K scopes may have equally good optics. However, the new Classic 4X test scope has excellent optics that give a full field that is exceptionally clear. There is very little fringe distortion and resolving power is good.

The %-inch clicks are sharp enough to feel easily and give about what you ask for, especially in changes of more than one inch. There was very little change in either windage or elevation when large amounts of the opposite adjustment were given. Both elevation and windage returned well to the zero setting after large changes had been made.

All in all, this scope performed very well indeed in shooting tests. I t should do equally as well under severe hunting conditions in any kind of weather, as

there was absolutely no sign of leaks when it was submerged for several minutes in 125-degree water, even with the caps off.

The price has been increased from the $46.95 tag on the Weaver K4 to $57.95 for the Classic 400. The Classic 300 and 600 sell for an even ten spot more than the same power in a K model scope. -Bob Hagel

Lyman Case Lube Kit

Lyman Gun Sight Co., now owned by The Leisure Group, Inc., has recently brought out a case resizing lubrication kit that contains everything needed for case resizing.

The kit is complete and contains a large lubrication pad measuring 4% x 7% inches, a generous 2-ounce squeeze tube of lubricant, and three brushes for cleaning and/or lubricating the inside of case necks. There is a wood handle threaded to take the brushes. I have used this kit for preparing several hundred cases for resizing, everything from .222 Remington cases to .300 Winchester Magnum brass, and results were excellent,

The large lube pad makes it possible to lube literally a handful of cases at one time by rolling them across the pad. In setting the pad up for use it is a good plan to spread a fairly good coat of lubricant on it evenly, then leave it open in a warm place and let the lube sink into the pad until it no longer appears smeared on the surface. This will avoid too much lube on the cases, which can cause wrinkled or dentedcases, shoulders. As the lubricant is worked deeper into the pad add a little more pressure as the cases are rolled, and they will lubricate very well for many, many cases.

The Lyman lubricant seems to be of very high quality and does a very good j o b of full length resizing with a minimum of pressure. I t does not require as much to do the j o b as some others that I have used, so there is less chance of deforming cases due to the lube creeping up in the die to the shoulder area.

The three brushes furnished with the kit are similar to bore brushes and

HANDLOADER - March-April. 1971

have the same size shank and thread. I n fact, bronze bore brushes can be used in the handle furnished with the kit. The brushes that are furnished appear to have nylon bristles, or some similar material. They do a good job of cleaning the inside of case necks. On the longer heavy case necks that sometimes give you fits in pulling out the expander button, the brush can be lubricated slightly by rolling it on the pad. Take it easy in this direction and don’t put enough lube o n the brush to “grease” the inside of the neck. Oil or grease does nothing good for powder. The three brushes will do the trick in case of all calibers normally used, from .22 to .45.

The kit may be bought from Lyman dealers for $5.25, and will last for many years and thousands of reloads. - Bob Hagel

Versamec 700 Shotshell Tool

Shotshell handloading requirements are almost as varied as night and day. The claybirder who regularly travels the skeet and trap circuits, expending ammo as if there will be no tomorrow, is generally best served by a high-capacity press that is precisely adjusted to handle one particular hull and a given set of components. But this approach is hardly suitable for the chap whose gunning pursuits demand assorted fodder ranging from light target loads in standard-length cases to the really stout prescriptions packaged in magnum-length hulls. His manifold needs place a premium on versatility rather than on strictly production-line performance.

There are, of course, several bench- type rigs on the market that fill this all-around niche, one of the newest being the Versamec 700 from Mayville Engineering Co., 1nc.-a firm that certainly needs no introduction t o the handloading clan.

Essentially, the single-stage Versamec 700 is a slightly modified version of the still-available MEC 600 J R shotshell press, itself a tool that is specially engineered to master plastic hulls. And for the benefit of the uninitiated who may scan these lines, the term “single- stage” means, simply, that the tool operator works with just one shell at a time, processing it through to

HANDLOADER - March-April. 1971

completion by moving it from one press station to the next.

Like the MEC 600 JR, the Versamec has five clockwise stations, the last three utilizing a plate-type shellholder for fast and positive positioning of the shell. Six press strokes are required to reload one shell.

The main difference, and really the only difference of note, between the 600 JR and the new Versamec involves a change at the shell reconditioning station. Here the Versamec features what MEC describes as the “platform cam.” The design change provides a longer stroke for ejecting the resizedl deprimed hull from the die. It’s a mechanical gem that absolutely eliminates the need for die adjustments when processing shells with different brass and basewad heights. In my trials, low-basewad shells having a brass height of one inch were ejected as reliably and as easily as those wearing minimum brass, such as Winchester and Remington plastic target hulls.

The availability of die sets for the Versamec runs full circle from .41O-bore through 10 gauge. The tool will also handle both 2 314 and 3-inch cases (2% and 3 in .4SO, and 2 718 and 3%-inch in S O gauge). Switching from standard length to the longer hulls requires the installation of a longer support tube at the reconditioning station, plus a spacer to lengthen the priming punch. The necessary extra clearance between the press base and the die-holder plate is achieved by removing a single bolt at the rear of the base and utilizing a different set of holes.

It is interesting to note that 3-inch shells can be resized and deprimed when the Versamec is set up for standard- length cases. However, once the main column is elevated, resizing magnum- length hulls fully to the rim of the brass cannot be accomplished unless the longer support tube is used.

MEC’s Pro-Check accessory, a stamped metal part that attaches t o the charge bar, is a standard item on the Versamec 700. Its foremost purpose is to keep the charge bar movements in proper sequence-to prevent accidental drop- ping of powder and shot charges. But its role is actually two-fold in that it also holds the vertical-sliding wad-guide assembly in proper contact with the shell mouth following powder charging.

In this capacity it helps t o speed up wad insertion.

Also a standard item on the Versamec is the Spindex crimp starting unit. Both 6 and 8-point “spinners” are included in the package, as well as a smooth-cone insert for use with previously-fired paper-tube shells. The 8-point spinner is self-aligning and unfailingly works t o perfection, while the 6-point must be manually indexed to mate with the original crimp folds. Both spinners do a very fine job of shaping the case mouth for final crimping.

The writer has never cared much for a smooth-cone crimp starter and this one does not prove to be the exception. It was tried with both Federal and Western Xpert once-fired paper-tube shells. Sometimes the original folds re-formed evenly, and sometimes they didn’t. The situation was about six of one and a half dozen of the other, and for my money I’ll take the 6-point spinner despite the need for manual indexing.

For starting the crimp on new, unfired 0 63

shells, both paper and plastic, the Spindex 6 and 8-point spinners will get the job done. But let’s face it-they do not produce the closely-spaced folds that are possible with the older type “star crimp” heads having “knife-edge” rather than rounded ribs.

When working with virgin Akan 3-inch plastic cases, for example, I tried the 6-point Spindex for starting the folds. Although the end result was a most serviceable crimp in every way, it was one in which I did not take a great deal of pride. The conspicuous gaps between the folds just didn’t appeal to my aesthetic side. But by replacing the Spindex unit with the old style starting head taken from my venerable MEC 400 (spacers required), I achieved a really first-class closure that in appearance exceeds even some factory offerings.

The versamec is fitted with MEC’s time-tried “Cam-Loc” crimping head. The design is such that the pressure required for coning, crimp closing and perimeter bevel are applied in separate stages, but all is accomplished, of course, with a single press stroke.

The Cam-Loc unit can be quickly and easily adjusted for both depth of closure and bevel. It should be noted that when switching from one type of plastic case to another a minor change in the cam setting will likely be necessary. The setting that produces the correct bevel 011 one type of hull is often too “heavy” for the next, and as such will cause the folds to close in a spiral fashion unless the setting is “lightened.”

During the three months that I’ve had a Versamec 700 with 12-gauge dies bolted to my bench, it has never balked once despite the wide and varied diet it’s been fed. Taken in stride were both 2 3/4 and 3-inch hulls, including paper- tube cases and just about every type of plastic case available.

So if it’s versatility that you’re looking for, along with loading ease, a quality reload and a right smart production rate, the Versamec very definitely merits your attention.

This bench-type tool wears a retail price tag of $82.50. Extra dies (in any gauge) are priced at $28 per set. More complete information may be obtained by contacting MEC, P. 0. Box 267, M a y d e , Wisconsin 53050.

--Wallace Labisky

Bushnell Sentry II Spotting Scope

Bushnell Optical Corporation has revised its Sentry prismatic spotting scope. The new scope, labeled the Sentry 11, is considerably more compact than the earlier version.

Finish is still the same non-reflective crackle coating of the original Sentry but a bit darker. The new scope is shorter than the older model with a length of 1 2 5/8 inches. Weight is almost the same, about 1% pounds.

The built-in tripod socket on the Sentry 11 is placed farther to the rear than on the older model, and is just forward of the prism housing in a flat-bottomed receptacle that protrudes slightly below the scope barrel. This, and the change in the shape of the prism housing, make the new scope less streamlined than the older scope.

The objective lens is inner shielded, which is supposed to eliminate the need for the pull-out lens shield found on the objective of the original Sentry. While this seems t o work quite well under normal conditions, 1 would still prefer a pull-out lens shade for looking into a low sun or in rain and snow.

All air-to-glass lens surfaces are coated to improve light transmission and cut reflection. The objective lens is still 50mm, which gives a bright field under even poor light conditions. I t was also found that the field is clear and quite distortion-free right out to the edges.

Eyepieces are available in 20X, 32X and 48X, and the eyepieces for the old a n d n e w S e n t r y s c o p e s a r e interchangable. The price of the Sentry II remains at the same attractive $54.50, and extra eyepieces in all powers sell for $19.50.

T h e new S e n t r y 11, l i k e i t s predecessor, is not only a good scope for spotting on the target range, but is light and compact enough to be an outstanding choice for big game trophy hunting where size and weight really count. -Bob Hagel 0

Reader By- Li nes

(Continued from Page 5 )

powder in the barrel. This was using a revolver with a six-inch bbl. I have not tried it in a four-inch, nor have I loaded any since that trial. Whether it will work out for anyone else I cannot say.

William R. Deal Piermont. N.H.

Secondary Explosion Effect

T h e Handloader is an excellent publication and I have enjoyed it very m u c h . A l t h o u g h I have b e e n handloading since 1932, I still find valuable information in every copy. However, I feel the information in T h e Handloader is gradually becoming more technical, which is fine for a certain percentage of your readers, but over the heads of a lot of us plain old shooters.

I believe the true facts of the “mythical secondary explosion effect” of reduced loads of slow burning p o w d e r s a r e contained within the excellent series of Pressure Factors articles. These factors, if kept in mind while reloading, could possibly chase away this problem which has so many people worried. When someone is able t o demonstrate that reduced loads do in fact create dangerous pressures I will believe it. In the meantime, I will simply watch case length, neck thickness, bullet vs. bore diameter, insure a clean bore and approach maximum loads with caution.

Robert Bruce, Jerome, Idaho 0

HANDLOADER - March-April. 1971 64