45_auto
Member
macgrumpy said:Not true, there is no movement of the firearm due to gas expansion until the bullet exits the muzzle. I'm sure everyone can agree that pressurized gas that is in a vessel will push with equal force in all directions. The bore of a firearm is simply a small diameter vessel and at any moment in time the pressure in the bore presses equally in all directions. We also know that when a force is opposed by an equal and opposite force the net force in either direction is zero, so that means that at any specific moment in time, while the bullet is in the bore, the net pressure in any direction is zero - there is no force in any direction that will cause the barrel to move, any movement is created by the shooter. When the bullet leaves the barrel the force pushing against the bolt face isn't opposed by an equal force so at that instant the weapon rotates around the body part that resists the unopposed force (rotating the firearm around your hand or shoulder). It's just like having a gas bottle in your garage, as long as the valve is closed and the gas is contained within the bottle nothing happens because the gas pressure is pushing in all directions with the same amount of force so the net force in any direction is zero. But if you were to knock the valve off the bottle then the bottle will take off like a rocket because the force of the gas against bottom of the bottle isn't being opposed by an equal and opposite force at the valve.
This is hilarious. If the force on the base of the bullet makes it move forward, what makes you think that the force on the breech face won't make the breech face move backwards?
I'm sure the Navy would like to talk to you, since by your theory a rail gun would have no recoil since it doesn't have any barrel pressure.
A paper on railgun recoil is here: http://kimerius.com/app/download/5784337080/Recoil+in+electromagnetic+railguns.pdf
Having established that electromagnetic railguns do indeed experience recoil forces in much the same way as conventional guns
About 400 years ago, a guy named "Slewton" or "Rewton" or something like that figured out that F=MA (Force = Mass x Acceleration) and a couple of other notions of motion. You can read about what NASA thinks about them here since you obviously never heard of them before: https://www.grc.nasa.gov/www/k-12/airplane/newton.html
The third law states that for every action (force) in nature there is an equal and opposite reaction. In other words, if object A exerts a force on object B, then object B also exerts an equal force on object A. Notice that the forces are exerted on different objects.
Pay particular attention to the third one (note that if there is a force accelerating your bullet towards the muzzle, there is an equal force accelerating your slide/barrel in the opposite direction.
The SAAMI paper on gun recoil is here: http://www.saami.org/PubResources/GunRecoilFormulae.pdf
Recoil can be described mathematically by the physical law of the Conservation of Momentum. The law states: "lf a force and it's reaction act between two bodies, and no other forces are present, equal and opposite changes in the momentum will be given to the two bodies." Simply stated, this says that for every action there is an equal and opposite (in direction) action
In the real world, this means that if your bullet is moving forward, your gun is moving backward. Since your grip is typically some given distance below the bore axis, this distance combined with the recoil force creates a rotational moment (Moment = Force x Distance) (also known as torque) that raises the barrel of the gun if you're shooting it in the normal position.
In most locked-breech semi-autos, the force is transmitted through the recoil spring into the frame during the time that the bullet is in the barrel. In a 1911, this distance is about 1/10 of an inch. If you compress your recoil spring to it's working length when the gun is fully in battery, then compress it an additional 1/10 of an inch, the force that it takes to compress it that additional 1/10 of an inch is the force that goes into the rotational moment to create the muzzle rise while the bullet is in the barrel. This is a fairly minimal amount, but as pointed out earlier, a few thousandths of an inch at the muzzle is significant at 25 yards.
In a revolver with no recoil spring to mitigate the transmission of recoil forces to the frame while the bullet is in the barrel, the recoil force of the bullet is immediately transmitted to the frame as soon as the bullet starts accelerating, which creates a much more powerful rotational moment while the bullet is in the barrel. This should be obvious by the additional height required on the front sight of a revolver versus a semi-automatic firing the same cartridge.
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