Airgun Ammunition Project

Team Members

Bryan LaMora

Joe Ouellette

Zach Rohlfs

Team 07F

Task: Provide an economical material to replace the current lead pellet.

Reason: Due to health concerns lead pellets will

eventually be discontinued.

Project Definition

Specifications

Pellet Size:

-.177 cal.

-.176 +.003/-.0005

-.4 to 10.5 grain

-.195” to .260” (ASTM F 590)

-Any Shape

Specifications

Requirements:

-minimum 24 lb shot force

-Non-Toxic

-100 ft/s to 1200 ft/s velocity range

--30 to 100 deg F operating temp.

-Immune to black oxide oils

-Remain intact after impact

-$.10 to $.80 per 100 pellet cost

-.835” @ 25yd Shot Group

Ideas & Evaluation

- All steel pellet

- Composite pellet

- BB encased in plastic

- Steel cylinder encased in plastic

- Plastic and Iron filings mix

Design Obstacles

-Metal and plastic composite

-Steel core

-Plastic exterior

Design Obstacles

•Sacrificed aerodynamics to increase weight

•Keeping the manufacturing process as simple as possible

Plastics Research

Requirements:

-Dense

-Impact resistant

-Fairly high melting point

-Inexpensive

-Easily molded or thermoformed

Plastic Body Material

- Criteria- Impact resistant at

low temperature- High density- Low cost- Easily injection

molded

- Material- Polypropylene- Polystyrene- PVC- ABS- Acrylic- Polyester- Nylon- Polyethylene- Fluoropolymers- Polycarbonate

Inner Material

- Criteria- Coefficient of

restitution- Density- Cost

- Materials- Aluminum - Nickel - Tin- Steel- Brass- Copper

Bounce Back Effect

- Lead: 55 Feet- Copper: 77 Feet- Brass: 105 Feet- Steel: 314 Feet

Bounce Back Results

Worst Case scenario coefficient of restitution: .22

Coefficient of restitution from tested : .106

Coefficient of restitution of lead: .16

Pellet Flight Characteristics

Will the velocities be approximately equal?

Is the Cd, coefficient of drag constant?

How do we determine the coefficient of drag?

What does this all mean?

Calculating Drag

AV

FC dd

2

21

Cd is the coefficient of

drag Fd is the force of drag is the density of the

fluid A is the cross-

sectional area. m is the mass of the

pellet ad is the acceleration

of drag V is the velocity of the

pellet at a given time, t

dd amF

dt

dVad

dx

dvVad

Fluent and approximations

Experimental data is not needed.

Small geometries need to be scaled by Reynolds numbers.

Two dimensional approximations differ from three dimensional.

Results and Their meaning

Cd~0.4 for hand calculations on the old pellet.

Cd~0.47 for the old pellet by Fluent using a two dimensional model.

Cd~0.56 for the new pellet by Fluent using a two dimensional model.

The velocity of the new pellet will degrade faster.

A) Pressure is constant through barrel.

B) Temperature decrease due to pressure change of gas is neglected.

C) Temperature is constant.

D) Force of gravity is negligible on pellet.

Calculation Assumptions

Pellet and Barrel

19.5”

.177”24 psi

Flow

Barrel: Brass 330

Rifling: 1 Twist in 14” Right Hand Lead

6 Lands .045” wide

Force due to Pressure

AC = Contact Area

CL = Contact Length

w = Width of Contact Area

FP = Force due to Pressure

P = Air Pressure in chamber

2.00553inC

A

)02(.277. ininCA

WLCCA

.277inLC

)6(045. inLC

.133lbPF

)200553(.2

24 ininlb

PF

CPAPF

Heat Generated by Friction

.0531lbf

F

)133)(.4(. lbfF

PFkfF

LB = Barrel Length

Wf = Work Due to Friction

FP = Force due to Pressure

DH = Change in Heat

lb.0863ftf

W

)121)(5.19)(0531(.inftinlb

fW

BLfF

fW

lb.0863ftΔΗ

f

W

Temperature Change

)( PCMwt = Material Weight

DH = Change in Heat

CP = Heat Capacity

DT = Change of Temp

Pellet Weight

Lead = .512g

Plastic = .0418g

Barrel weight

Brass 330 = 185.07g

TLead Pellet = 1.77 C

TPlastic Pellet = 1.49 C

TBarrel = .0017 C

)(

))((

wtMPC

wtMPC

Wk Mon Tues Wed Thur FriMarch1 10-14 First Day Back

2 17-21 Quarter Time Line update Empire update

3 24-28April 4 31-04 <-------------------------Tooling Setup---------------------------> Crosman Update Meeting

5 07-11 <---------------------------------------------Machining of f irst 7 pellets-------------------------------------------------------><--------Testing #1--------->6 14-18 <---------------------------------------------Machining of 40 new prototypes------------------------------------------------>

7 21-25 <--------Testing #2--------->May 8 28-02 <----------------------------------Technical paper edit------------------------------------------>Tech paper to Advisor for review .

9 05-09 <-----------Technical paper f inal edit--------------> Technical paper Turn in. Set up test f iring Pellet Firing Demonstration

10 12-16 <------------------------------Creation: poster/presentation-----------------------------> Deliverables w rap up Final Presentation

Prototyping & Testing Schedule

Conclusions

The new Pellet met the following criteria: Functions in a .177 cal Air Rifle. Between 4 and 10 grains in weight. .255 in length Operates in a velocity range of 100 to 1200

ft/sec. Nontoxic and resistant to black oxide. Low Bounce back.

Conclusions

The new Pellet fell short in the following areas: Utilize rifling in barrel:

Plastic did not conform to the rifling of the barrel.Under-sizing of pellet “skirt” will help pellet follow

rifling.

Accuracy:The lack of spin of the pellet out of the barrel.

Intact after impact:Prototype was hand machined, plastic did not “lock”

core into pellet.

Questions?