Air Rifle Reality

7/27/2019 Air Rifle Reality

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Airgun Pellet Flight

Velocity - Accuracy Value. And the search for efficiency via goodengineering.

Note: The subject matter here concerns reality. Our intense

commitment to marketing has distorted American law into politics -that concentrates upon illusion, and momentary opinions instead.Basically, attempting to add whistles and bells in the hope ofpoliticizing natural laws, is just another futile attempt to lurehumans to act like lemmings i.e. leaping into the sea of BS. Again wehave another attempt to point the finger at a democratic majoritydemanding the insanity of overruling engineers in order to make thembuild dangerous automobiles (for example), and then patch the dangerwith somewhat successful kludges to raise things to the next level ofmore engineered kludges; without ever really fixing the basic problemof a public; that lives for excessively brainwashed SPEED!

Velocity - Accuracy - ValueSome things to look for in an airgun.

By Tom Gaylordexclusively for PyramydAir.com. Copyright 2003 All Rights Reserved

VELOCITY AND PELLETS

It seems fantastic that an air rifle can launch a pellet faster than1,200 feet per second (f.p.s.), but some powerful rifles can.However, just because it's possible to do it doesn't mean that it'salso desirable. In fact, it isn't. To understand why, you mustunderstand how a modern pellet works.

Diabolos

The classic diabolo pellet has a pinched waist and a hollow skirt.The shape of the nose can be round, pointed, flat or anything else.The skirt can be thick or thin - long or short. All these variablesaffect the flight of the pellet somewhat, but the basic diabolo shapeis what affects it the most. These .22-caliber Benjamin-Sheridanpellets are very similar to Crosman's Premier design.

Most top-quality pellets are made with a pinched waist - a so-called wasp waist. The correct term for this design is diabolo. Adiabolo pellet is stabilized (prevented from tumbling) by the highair drag on its tail. A hollow skirt plus the pinched waist worktogether to produce this drag, plus a forward weight bias keeps the


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nose pointed in the right direction. Where a conventional riflestabilizes the bullet by spinning it rapidly, a diabolo pellet willeven be reasonably accurate in a smoothbore gun. It works exactlylike badminton "birdie" and for the same reason - a high-drag skirt.Most modern pellet rifles and pistols are rifled which does cause thepellet to spin on its axis in flight, but the rate of spin is too

slow to stabilize the pellet by itself. When the pellet leaves themuzzle it starts slowing down very rapidly. It will lose more thanhalf its muzzle velocity within the first 100 yards of flight. If thepellet was shot at a speed above the sound barrier, it will also bedestabilized by passing through the sonic pressure wave it created.The sound barrier varies, but it usually remains near 1,100 f.p.s. atsea level on a normal day. When a pellet goes faster than the soundbarrier it makes a sharp crack, which is the "breaking" of thebarrier. It will be less accurate than if it were shot from the samegun at 900 f.p.s. or less, where the sound barrier is not a problem.While 900 f.p.s. is quite a bit below 1,100 f.p.s., there is great

turbulence whenever the sonic barrier is approached. For this reason,knowledgeable shooters never allow their pellet rifles to shoot muchfaster than 900 f.p.s. If they buy one of the supermagnums that doshoot much faster, they use the heaviest pellets they can find to getthe muzzle velocity back down.

Match King Boat TailMissiles that travel faster than the speed of sound slow down

much faster than missiles going slower than the speed of sound. Toretain their velocity, supersonic missiles must be very aerodynamic,

while slower missiles are less aerodynamic.

On the low end of the scale, Olympic target airguns seldom shootpellets as fast as 600 f.p.s., yet they will outshoot almost anyother pellet gun at short ranges. The target air pistols are nearlyas fast as the target rifles - ranging from 450 f.p.s. to 580 f.p.s.Both target rifles and pistols shoot wadcutter pellets with flatnoses that cut perfect holes in target paper. Wadcutters are theleast aerodynamic pellets on the market, but since the target gunsdon't shoot very fast, it doesn't matter. Most hunters want a riflethat will shoot a large heavy pellet accurately at 750 to 900 f.p.s.

Most general shooters - the so-called plinkers - want to shoot at 600to 900 f.p.s. with a rifle and 350 to 550 f.p.s. with a pistol. Highvelocity does not mean high quality or accuracy. If fact, it mightmean just the opposite. The diabolo pellet is designed to give thegreatest accuracy at speeds well below the sound barrier, so selectyour airguns accordingly.The boattail pointed bullet is designed for supersonic flight at alltimes. This is a Sierra MatchKing, which is one of the top targetbullets in the world. It is made of a copper jacket around a lead


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core with a tiny opening in the point. They come in all popularcalibers, but this .30 caliber 168-grain bullet is what made the linefamous. It's used for long-range target shooting, primarily.

WHAT ABOUT SOLID PELLETS?

Okay - if hollow-tail wasp-waisted pellets aren't accurate above thesound barrier, what about solid lead "pellets?" Several brands ofthese interesting "pellets" are now available, but do they give theaccuracy you require? Another name for these solid pellets isbullets, because that's exactly what they are. So what works forbullets also works for solid pellets.

These are both .22-caliber pellets. The 30-grain pellet on the leftis a solid lead pellet from PelletMan. The lack of a hollow skirt anda wasp waist means this pellet has to spin faster to stabilize in

flight. Than means it must be shot faster than a normal pellet. Ithas a cupped base, plus there is a larger-diameter driving bandaround the base to take the rifling and seal the bore. The CrosmanPremier diabolo on the right weighs 14.3 grains.

As it turns out, .22 long rifle ammunition, which fires a 40-grain lead bullet, is ALSO less accurate if the bullet goessupersonic. Why? Because when it is just barely supersonic, as most .22 LR high-speed ammo is, the bullet gets tossed around by its ownsonic wave. To get around this, a bullet has to be extremelystreamlined and it needs to be shot at several times the speed ofsound. So, if you can get your solid pellets out the muzzle at 1,400

f.p.s. and faster, there may be an advantage. Less than that and youare tossing away accuracy. That's why all .22 rimfire target ammo issubsonic. Learn from the target shooters and stay well under thesound barrier. If you do shoot solid pellets, remember that they mustgo faster to stabilize because they don't have the high drag of thehollow tail. The spin imparted by the rifling must stabilize them.

BUT DOESN'T A FASTER PELLET DROP LESS ON ITS WAY TO THE TARGET?

Yes, it does. It also wanders all over the place instead of tracking

along an accurate path. So you can either hit your target with theslower pellet or you can miss it with a faster pellet that doesn'tdrop as much - it's your choice. Back in the late 1800s, men shot at1,000 yards and even out to one mile with bullets that barely wentsupersonic, if at all. They had to judge the range more than shootersdo today, but their rifles were very accurate. The bullet that hitsthe target does more damage than the one that misses at highvelocity.


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SO, ARE THE SUPERFAST AIR RIFLES BAD?

Not at all! They're great - especially if you need extra power forhunting and long-range shooting. But use them correctly. Match theirhigh power with heavy pellets so you get all the accuracy they haveto offer. For example, a Gamo 1250 will shoot over 1,200 f.p.s. in .

177 caliber with the lightest pellets. RWS Hobbys weigh about 6.9grains and Skenco lead-free pellets are more than a full grainlighter. You would not use them in a 1250 because they are too light.Instead, use a Beeman Kodiak/H&N Barracuda (same pellet) that weighs10.6 grains or a Crosman Premier 10.5-grain pellet. These will bothslow the velocity down to somewhere in the 1,000 f.p.s. region wherethe rifle can do its best. If you have a choice of calibers, such aswith the RWS 350 Magnum, which comes in both .177 and .22, get the .22 and use the heavier pellets. You will get all the smashing powerthe powerplant has to offer. If you absolutely must have a .177 inone of the super-powerful rifles, always match it with the heaviest

pellets for the caliber.

CONCLUSIONS:

Airgun quality does not come from velocity. It comes from accuracy,smooth operation, good design and quality control and other factors.Don't allow velocity alone to rule your airgun choices because if youdo, you will miss most of what is good about this hobby.

.177 is generally used for target shooting although it is suitablefor small birds etc. The problem with .177 is this and I'm making

assumptions thata) you live in the UK or Canada, andb) you don't have a firearms certificate.If I'm wrong about either feel free to correct me. .177 is a tinypellet with very good penetrating qualities. However they tend topass all the way through many targets including rabbits pigeons etc.Whilst that may sound good it actually means your wasting energy thatneeds to be transferred to the target in order to achieve a cleanquick kill. As a limit you only have 12ft/lbs of muzzle energy toplay with unless you posses a firearms certificate (and even less bythe time the pellet strikes its target) so its important that all its

energy is expended on the target not just some as it keeps ontraveling out the other side. .177 is excellent for target shootingbecause of the higher velocities achieved (approx 800 feet per secondat 12ft/lbs) giving a flatter trajectory over a given distance.

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Al's Note: A consistent demonstration of judgment here is for avelocity range of 600 to 800 fps muzzle velocity - to maintain


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accuracy, and overall stability of a shooting program/system withinan airgun's true limitations. I believe the expertise will agree thatthis is a true statement for the entire scope of pellet guns -regardless of caliber; due to rifling and lead usage, and diabolo airflow technology. This is truly an area best left in the hands ofengineers, rather then the responding to the whims of the general

public. ************************

The .22, on the other hand, is a bigger pellet with a slower velocity(600fps ish at 12ft/lbs) it has less penetrating capability but asmentioned this is a good thing when hunting live quarry as the pelletis less likely to pass through the target and therefore delivers allits energy to the target making a clean quick efficient kill morelikely. On the downside as pellet velocities in .22 are lower thepellet presents a more curved trajectory making accurate shootingmore difficult as greater compensations for elevation have to be made

when shooting above or below the range for which the rifle is zeroed.There are pros and cons to either caliber but as a generalization Iwould say if you intend shooting Pepsi cans and chalk targets buy a .177. If you enjoy flattening rabbits and crows etc buy a .22. I tendto use a Daisy (easy pumper), or old Marksman break-barrel for tincan plinking, and a Sheridan 177 or a cheap (beater) Chinese 22 underlever service training rifle for hunting (via NRA position shootingwith open sights (in spite of aperture preference) i.e. bigaperture). I do enjoy a Benjamin CO2 22 pistol (with shoulder stock)that requires more shooting skill for the 600 FPS muzzle velocity;for a noisy 6 inch barrel. Then again, I am a NRA CPI, and retired

engineer - making me a bit of a curmudgeon by todays standards.

In external ballistics, point-blank range is the distance between afirearm and a target of a given size such that the bullet in flightis expected to strike the target without adjusting the elevation ofthe firearm. The point-blank range will vary with the firearm and itsparticular ballistic characteristics, as well as the dimension oftarget chosen. A firearm with a flatter trajectory will permit afarther maximum point-blank range for a given target size, while alarger target will allow for a longer point-blank range for a givenset of ballistics.

Modern delusional concepts masks the limitations for application onhunted targets - with low velocity weapons (under 900 FPS). Inforensics, and now popular usage, point-blank range has come to meanextremely close range (i.e., target within about a meter (3 ft) ofthe muzzle at moment of discharge, but not close enough to be anactual contact shot). My evaluation of "point blank" with 300 FPSweapons(archery and Daisy BB guns) and tin can size targets, is that10 meters is a realistic limit for point blank shooting that is


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mechanically efficient as my 6mm is out to 300 meters on deer sizetargets [relativity]. Now using 800 FPS weapons point blank range isincreased to 16 meters. One has to bare in mind that the reasonabledistance of 54 feet maintains the ballistic efficiency of theprojectile for proper performance i.e. without stretching limitbeyond +30%. [Experimenting was done with a Sheridan pump using pump

strokes for velocity control; and blank paper targets for center ofmass holding, for group size recordings. Winds calm, and time basefor "gathering data" approximately one year. The Dallas Pistol Clubgave me the opportunity to shoot my 1100 FPS Diana 37 at 25 and 50yards, to verify my weaker unpropitious concept of range.[I currently am weakening my mainspring to tone down the poor showingof 50 yard groups, and applying the theology of the Hawkin rifle; ata max range of 20 meters - to gain a more controlled humaneextermination.]

Pellet Deceleration: Here is a point that is not discussed by those

deluded with mo-power. Now that I am more civilized, I find that alot of areas that I shoot over have a grass base, leading into tuftsof woodland, so I have checked out grass surface ricochets, to findout that the typical earth drag, plus foliage, kills velocity rapidlyenough for a safety band of 100yds to exist - as a typical invisiblebackstop concern.

So to finalize: I hope this message opens the door toredeveloping the art of shooting sports, and regain the concept ofposition shooting instead of setting up tripods and rifle scopes ofmore than 2.5 power (my favorite Leopold that is still mounted upon

my Ruger 22 bolt rifle) and other paraphernalia. Totally destroyingmobility, My Cherokee background wants to travel in the woodscarrying my light rifle, spot game, solidify position for a humaneaccurate shot. If more than 20 meters, stalk it.

When realistically limited to 600 fps with a Diabolo pellet, allthe current high tech philosophy is BS. Rifling just assists a 'sluggun' by finessement; however, arrow dynamics is the prime control,and sufficient for a maximum working range of 75 feet with less than(an adequate) 3 minute dispersion grouping (i.e. without aninterfering breeze). [A taste of honesty?]

The sound barrier is breached!Until the 1980s, peak pellet velocities remained below about 870f.p.s. In the early 80s, several rifles finally achieved 1,000f.p.s. Soon after that, British airgun designer Ivan Hancock brokethe sound barrier with his Mach I breakbarrel springer that got over1,150 f.p.s. in .177 caliber. After that, things changed very fast.

Suddenly, accuracy was out the window, as shooters discovered thatthe diabolo shape is not well-suited to flight in the transonic orsupersonic region. The fact that the pellet remains at this high


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velocity for only a few yards makes no difference. The damage wasdone. The extreme buffeting caused when the pellet reaches and passestransonic speed, then slows back down and goes through it again ismore than enough to destabilize it and cause groups to open.

Sales go crazy!However, the other side of the coin is that high velocity sells guns.

A company that advertises their gun shoots 1,000fps and higherattracts lots of attention and, yes, sales. In fact, so muchattention has been given to 1,000fps that it is now seen as themarketing kiss of death to advertise anything less. Some companieshave gone to great lengths to tout ever-higher velocities without athought being given to accuracy. Special lightweight, lead-freepellets are now selling well partly because of the velocity boostthey give to the guns that shoot them. Again purchasing a qualityairgun that is light for hunting, and quick position shooting,without a lot of paraphernalia, or concern for objects that are 200yards away. One that cocks easily so that teaching younger siblings

the true adventure of shooting sports, instead of ego blossoming.

This Diana 25 smoothbore was made in World War II.

Todays blog falls under the heading, Its not always a good idea to try everything. Back when wewere exploring the Diana 25 smoothbore airgun, we saw how incredibly accurate it was with certainpellets at 10 meters.

This 10-shot group of JSB Exact RS pellets was shot at 10 meters. The extreme spread measures just0.337 inches between centers! It made us all wonder just how accurate a smoothbore pellet gun can

be.

When I backed up to 25 yards, however, the groups opened up to between 2.5 and 3+ inches for the

same pellet. Obviously, the pellet needs to be stabilized by both the high drag of its diabolo shape andby the spin introduced by rifling. Drag, alone, is not enough to stabilize the pellet at ranges beyond 20yards. [My mechanical limit for humane kills, and was true in archery distances over 25 yards needinghelical pitch for vanes. Apparently flight is affected by aerodynamic bubble theory that is broken up bychanging surfaces.]

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