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Uncl: gun barrel



This question came up years ago in one of my classes. A member of the class was
GOOOOD competition shooter (roomfull of cups). She explained that there was a
n optimum load for a particular barrel length. This load depends on barrel len
gth, size of powder granual, make of powder, age of powder, make of barrel, num
ber of times the barrel has been used, caliber, make of gun and how you hold yo
ur mouth (Okay I added the last one). She did not know any formulas just adjus
ted the load by feel and experience. Further discussion and some research (gun
magazineshave a vocabulary which is almost as obtuse as educational journals)
revealed that the optimum load/length is achieved when the bullet has a zero ac
celeration as it exits the barrel. Thrust-Friction = 0. If Thrust is greater t
han friction the expanding gas cloud that leaves the barrel with the bullet thr
ows the bullet off course. If Friction is greater than thrust the bullet slows
down in the barrel and the bullet drops farther than expected during the fligh
t and misses the bull. Most modern guns are designed such that the bullet has
zero acceleration when it leaves the barrel Thus changing the length of the bar
rel of a modern firearm (rifles especially) almost always result in a decrease
in performance. As usual there is an exception, the .22 caliber long is acceler
ating as the bullet leaves the barrel thus wasting lots of energy. (Not an exci
ting piece of knowlege but usefull in a trivia contest in our part of the world

Don Mathieson________________dmathie@vm.tulsa.cc.ok.us
Tulsa Community College______918-595-7485
3727 East Apache
Tulsa, Oklahoma 74115