Julie Worth said:
Unfortunately, this is all wrong. Oxygen is not needed as the powder contains its own oxidizer. And no, the air in the barrel has little to do with recoil. It does decrease the speed of the bullet slightly, so that reduces the recoil slightly, but not enough to matter.
Well, yes and no. I didn't mean to say the gunpowerder wouldn't burn at all. It does. But having its own oxidizer does not means it burns as fast, or builds up enough external gasses to propel a bullet at several hundred feet per second. The air inside a cartridge makes a big difference. Try firing one in a vacumm, with a vacuum packed cartridge, and see what happens. There's also a noticable difference in recoil when a weapon is fired in a vacuum.
Recoil is significantly less when fired in a vacuum, and it is because of the air in the barrel. It's not only the friction, it's the conpressed air wave caused by the friction. The air inside the barrel makes the bullet itself act as if it had more mass. I've fired pistols in vacumms, and the difference in recoil is quite noticeable. If there's another cause of the difference in recoil, no one I know can determine what it is.
This does depend on bullet type. A pointed bullet is much less affected, a round bullet with a big hollowpoint is affected to a much greater extent.
It's not nearly as bad as the silly scene in Firefly where they pumped oxygen into a gun barrel in order to make it fire at all, but both factors do make a very real difference.
Of course, when you fire a weapon in space, you won't be propelled straight back at all. What will happen is that most of the energy will be utilized in spinning you about your axis. There is backward motion, but how much is very difficult to determine because it all depends on where and how you hold the weapon.
Recoil is also affected by how tightly the bullet is being squeezed by the brass casing, which also makes teh bullet act as if it had more or less mass, by bullet diameter in relation to land and groove diameter, and even by the number of grooves.
There are two "kinds" of recoil, real and apparent. Real is a straight scientific value of mass and energy. Apparent is all these other factors, and they do affect recoil significantly. "Real" doesn't happen unless you remove all other factors. "Apparent" is what a shooter actually deals with.