Home Forums Hunting & Shooting Ask The Gunwriters Recoil and short barrels

The exiting gasses have exactly the same mass as the powder that was burned to generate them. 50 grains of powder = 50 grains of gas plus particulates.... else matter is not conserved. SeanD has it right.

You are right, same mass, what I should have said is that the volume and therefore mass of gasses is so dispersed it has little effect on recoil as it exits the barrel.

Momentum is defined as mass x velocity.

Force is the first derivative of momentum, F=d(mv)/dt.

Only mass, velocity, and time enter into the equations. There is no term for "dispersed", nor should there be. 50 grams of gas has the same effect on force and momentum as 50 grams of lead, all other factors equal.

I have a little information from two sources, both old reloading manuals. Actual exit velocity of gases from a firearm is measured with a "Sebert Velocimeter" at an average of 4,700 feet per second for the center of mass of the powder gases according to Lyman Manual #47. Another source, Hatcher's Notebook, states that a constant can be used to approximate the change for different pressure systems, using a "k" factor of 1.25 for shotguns and low pressure handguns, 1.5 for magnum handguns and 1.75 high pressure(>45,000 psi) firearms. Recoil velocity of the firearm= [Wb + (k x c)] x Vb all divided by Weight of gun. If this "K" varies that much, the average velocity of the gasses must vary by as much, if Hatcher is correct. "c" is powder weight in pounds, Wb is weight of bullet and Vb is velocity of the bullet. I use 4700 fps for rifles, 4000 fps for pistols and 3350 fps for shotguns, just to make some accomodation when using the traditional free recoil energy and velocity formulas.

We often hear that the propellant gases travel at half the speed of the bullet. That's not exactly true. What is meant by this is that one end of the gas column moves at the speed of the bullet, while the bullet remains in the barrel, and that the other end stays put at the rear of the cartridge case. Therefore the center of mass of the gas column does move at one half the speed of the bullet, while the bullet remains in the barrel.

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How can you seperate the two forces at this time? Recoil-V-rocket effect.

We need recoil numbers from a railgun to compare with.

Denton,

Spring has arrived in my parts. What's the latest on your experiment?

GM

I have the measurement equipment, and the snow is off the range. Unfortunately, I also have a six week work assignment in Virginia, and it looks like a three week gig in Taiwan... Either I have time, or I have money, but I never seem to have both.