Physics of recoil question

[Skeptic10787]

I was watching one of those "worlds dumbest videos" type shows tonight and one video posed a question in my mind about recoil.

The video was the one where the idiot props his ladder up against a tree branch next to a pool, climbs to the top, tries to jump outward off the ladder so as to land in the pool, but the force pushes the branch back and the idiot plops to the ground. It really was quite amusing.
To the question.
Lets say the ladder is a firearm, the tree branch is a shooters shoulder (or hand), and the idiot is the bullet. Going by the same physics demonstrated in the video, would it be true to say that when a shooter fires a gun, velocity is lost in recoil? Would the velocity be higher in a firearm that is mounted sturdy, vs one allowed to recoil? Or is the amount of velocity lost just not significant enough to matter.

[kyote]

dang all..as I scratch my head..I am wondering now if this would hold true for a .22 rim fire rifle with a bull barrel?

[Don Fischer]

It would be my guess that by the time recoil starts that the bullet has exited the barrel. Think a moment, if it hadn't, then the bullet would shoot well over the intended target.

[jpsmith1]

I've always been under the impression that the bullet is long gone before recoil can affect it.

[dave375hh]

Sorry but recoil starts as soon as the cartrige fires. That's why light/fast bullets in a handgun shoot lower on a target than heavy/slower bullet, given the same sight setting. The slower bullet has more time to act on the barrel causing muzzle rise. That's also why SxS shotguns are made to cross their patterns at about 40 yards. If the recoil didn't start as soon it would be impossible to "limp wrist" a semiauto pistol into a failure to feed or eject, and this does happen.
That radio DJ on the ladder was an extremely slow action reaction compared to discharging a gun. The time is what slowed him down. A difference of seconds as opposed to miliseconds, the longer the action/reaction the greater the deflection.

[jro45]

To my way of thinking. I beleave the bullet is out the barrel by the time the rifle comes back to give you recoil. Unless you are shooting very slow bullets that just make it out the barrel but then you would not feel the recoil it would be so little.

[Slamfire]

Sorry but recoil starts as soon as the cartrige fires. That's why light/fast bullets in a handgun shoot lower on a target than heavy/slower bullet, given the same sight setting. The slower bullet has more time to act on the barrel causing muzzle rise. That's also why SxS shotguns are made to cross their patterns at about 40 yards. If the recoil didn't start as soon it would be impossible to "limp wrist" a semiauto pistol into a failure to feed or eject, and this does happen.
That radio DJ on the ladder was an extremely slow action reaction compared to discharging a gun. The time is what slowed him down. A difference of seconds as opposed to miliseconds, the longer the action/reaction the greater the deflection.

That's certainly true at 1000 fps, or less, but in the case of 3000 fps or more, is it still true? Doesn't the greater mass of the rifle, lead to more inertia, retarding the movement to the rear?

[sgtt]

You may wish to read Newton's laws.  It starts at the same time.  Now.  The "felt" or preceived recoil is another matter.

[R.W.Dale]

 Bear in mind that probably 70% of precieved recoil in a rifle cartrige is NOT due to the bullets acceleration, but is a result of the rapidly expanding high velocity gasses pushing the rifle into your shoulder like a rocket after the bullet clears the muzzle. This is why muzzle brakes can be so effective but also why they have no effect on reducing the inital recoil pulse.

[The Sodbuster]

Skeptic10787 asked:

would it be true to say that when a shooter fires a gun, velocity is lost in recoil? Would the velocity be higher in a firearm that is mounted sturdy, vs one allowed to recoil?

There's no escaping conservation of momentum.  If the rifle is mounted on a sled that can roll back with recoil, bullet velocity will be the same as if the rifle were secured to a 3 ton stone.  Recoil is the same in both cases, but the stones greater mass "absorbs" more recoil.  Momentum is mass X velocity.  In the first case the sled has relatively little mass (and little friction) and the rifle/sled combo rolls back some distance.  In the second case, the tremendous mass of the rifle/stone combo means the velocity imparted to the stone will be very small.  For all practical purposes, the stone doesn't move.  Bullet velocity is a function of the force applied to the bullet (dependent on powder amount and type, barrel length, chamber "tightness", primer, etc.).  Securing the rifle into a rigid platform won't change that.

To answer your question: No, velocity is not lost in recoil.  Increasing the weight of the gun or securing the gun to a fixed platform will reduce the amount transferred to you, the shooter; but the rifles momentum won't change.  Krochus is on target about a portion of recoil being due to the mass of gas exiting the barrel and that a muzzle brake that diverts that gas perpindicular to the bore will reduce the amount of recoil the shooter absorbs.

[darrell8937]

recoil starts at the moment the bullets starts to move. The bullet accelerates dowb the bore. If the rifle weighed as little as the bullet(equal mass) Than the total energy would be divided equally between the gun and the bullet so the gun and the bullet would travel away from each other at equal speed. half of the speed, than if ithe bullet opposed a inmovable object. But of course that is not the case , that would be a tiny little rifle. The mass of the rifle allows the recoil/acceleration of the bullet to be transfered into the mass of the rifle and you. If you were to suspend a rifle on a string in mid air and rig a remote trigger and fire. the rifle would shot back wards a bit. bullet velocity would be reduced somewhat. The lighter the rifle the greater velocity loss. In the practcal world where rifles are heavy enough to make them at least bearable to shoot , the velocity loss is not that great! Recoil is absoured in two ways, absourbed into mass and transfered into time. A rocket engine works the same. No bullet but resistance gases. and it burns longer. In short. yes. velocity decreases the less the rifle is supported to oppose the opposite direction. This is a great lab expirment or a lot of fun math, but in the world of firearms not too useful! For maxium velocity.. max rifle weight and a big fat shooter. this can all be seen in algebra. Rember that course that seemed to have no use. well it does.

[darrell8937]

P>S.
To mount a rifle ridgidly. for instance removing the stock. no reciever. just a barrell with a closed brech and some means of igniting the charge,, basicly a cannon. and mounting against a two ton steel block.  virtualy an imovable object. This would be very bad. the opposing force from the acceleration would have no place to disapate except for time. the barrell would likley blow apart from stress. In heavy artillery , there are spades droped into the ground,  soft earth. If you were to wedge the spade against say a large rock. things start to break and get dangerous. this opposing energy must be managed! Just as when you apply the brakes on you car, the enegy of movement(kinietc) is not lost. it is transfered into heat and disapated in to the atmosphere. We can only change the forces involved , we can not elimenate them.