The discussion centers on the impact of placing a gun against an immovable wall when fired, specifically regarding the momentum and velocity of the bullet. It is established that if the gun and bullet have equal mass, the bullet's velocity may increase when the gun is restrained, as the energy from the propellant gasses is fully transferred to the bullet instead of being split between the bullet and the recoiling gun. The speed of sound in the propellant gases and the gun's frame plays a crucial role in determining how quickly the wall's effect can influence the bullet's velocity. Overall, fixing the gun against a wall maximizes the energy transferred to the bullet, potentially doubling its velocity.
PREREQUISITESThis discussion is beneficial for physicists, firearms enthusiasts, ballistics experts, and anyone interested in the dynamics of gun recoil and its effects on bullet performance.
Keep in mind that the total momentum has to include the gas leaving the barrel. The Lyman reloading book has the estimate in their equations and you can also find it with a web search. It is common for the gas to add 20% to the momentum.RobRobinette said:I used QuickLOAD, an internal ballistics calculator, to calculate some in-barrel bullet speeds. For a 357 Magnum pistol with a 4 inch barrel firing a 180 grain bullet, the bullet is going 200 ms at 2 inches down the barrel and 291 ms at the 4" muzzle. I googled the speed of sound through metal at 5960 ms.
It appears the shock wave through the metal frame will be almost instantaneous so I'm thinking the bullet's velocity will be affected, but by how much?