TargetTalk

Is recoil in the form of muzzle displacement from the original state noticed as the projectile leaves the barrel (or shortly after it does) i.e having no effect on the trajectory or is it progressively felt as the projectile accelerates down the barrel? Years ago a rifle shooter told me it was the latter but I am not so sure that I agree with him.

Brilliant videos of semi-auto .22s at http://karlslundesport.dk/default.asp?A ... u&Item=114 will show that for a semi-auto most of the recoil is well after the projectile has left the barrel.
The recoil characteristics of a single-shot (or revolver) will differ in the time/movement profile, but effectively give the same overall recoil if the barrel height, grip shape and weighting of the firearm are similar.

Only the recoil while the projectile is in the barrel can affect the trajectory

When is it 'felt'? - about 1/10th second after it has happened

Spencer

I think you guys are pairing to different aspects of reaction. There's recoil which is the equally opposite reaction to the projectile being propelled down the barrel which is at the same instant that the projectile is fired, and then there is muzzle flip which has to do with the exit of the projectile from th barrel.

The laws of physics say that the reaction to the projectile being propelled while the projectile is still in the barrel. The full felt effects are delay because the force is used to move the bolt and such, but the process starts upon firing.

Then again you guys are in Australia, and we know the rules are different there, the water in the toilet even rotates backwards ;)

Richard H wrote:I think you guys are pairing to different aspects of reaction. There's recoil which is the equally opposite reaction to the projectile being propelled down the barrel which is at the same instant that the projectile is fired, and then there is muzzle flip which has to do with the exit of the projectile from th barrel.

The laws of physics say that the reaction to the projectile being propelled while the projectile is still in the barrel. The full felt effects are delay because the force is used to move the bolt and such, but the process starts upon firing.

Then again you guys are in Australia, and we know the rules are different there, the water in the toilet even rotates backwards ;)

The original post asked about 'recoil in the form of muzzle displacement'.
Muzzle flip will consist of a number of factors, but in an ISSF Standard Pistol the muzzle flip immediately after the projectile leaves the barrel is a comparatively minor factor; most of the muzzle flip is after the projectile has departed downrange.

Action = reaction: remember? The force acting forwards on the bullet is equal to the force acting backwards on the base of the case. Let's ignore chamber and barrel friction. If the case has to stay in the chamber because the breech remains closed, the gun starts to recoil as soon as the bullet starts to move forwards. The gun's acceleration is much lower, however, in inverse proportion to its mass versus the bullet's mass. With a high barrel line, the gun is more or less constrained below the barrel line, so starts to rotate (the 'muzzle flip'). Muzzle blast adds to the recoil force acting on the gun, but this, of course, happens as the bullet leaves. Thus a fixed-breech gun starts moving as soon as ignition occurs.

In a blow-back action, as shown elegantly by the videos mentioned above, the case is free to move backwards, pushing the slide backwards. Acceleration of case + slide effectively reacts the force on the bullet, so the gun does not have to move, at least whilst the slide is moving. However, compression of the recoil spring and cocking the hammer transfer forces to the gun's frame, so will move the gun to some extent. When the slide hits the stop at its rearward extent of movement, its momentum is shared between the slide and the gun, so the gun is jolted backwards. This will be long after the bullet has left the barrel.

Look at the videos: some pistols seem to move more than others before the slide hits the stop. I suppose this reflects different recoil spring resistance and hammer-cocking mechanisms.

When do you feel the recoil? Probably as the bullet hits the target - reactions are sooo slow!

Richard H wrote:...Then again you guys are in Australia, and we know the rules are different there, the water in the toilet even rotates backwards ;)

This from somebody who drives on the wrong side of the road???
Spencer ;)>

Does this mean that if there was a blow back design for free pistol shooting, it would be more "forgiving", score-wise for the average shooter?

Ron

ronpistolero wrote:Does this mean that if there was a blow back design for free pistol shooting, it would be more "forgiving", score-wise for the average shooter?

Ron

Maybe

ronpistolero wrote:Does this mean that if there was a blow back design for free pistol shooting, it would be more "forgiving", score-wise for the average shooter?

Ron

I'm fairly new to the target shooting discipline, but when a pistol is "sighted", by definition you automatically compensate for any recoil/mussle flip that occurs while the bullet is still in the barrel. Correct? As for the drilled barrels of the Steyr LP10/LP50 and other so-called "compensators", it seems to me that attempts to reduce these movements would be most advantageous in rapid fire events, where a quick re-acquisition of the target is of prime importance.

superstring wrote:

ronpistolero wrote:Does this mean that if there was a blow back design for free pistol shooting, it would be more "forgiving", score-wise for the average shooter?

Ron

I'm fairly new to the target shooting discipline, but when a pistol is "sighted", by definition you automatically compensate for any recoil/mussle flip that occurs while the bullet is still in the barrel. Correct? As for the drilled barrels of the Steyr LP10/LP50 and other so-called "compensators", it seems to me that attempts to reduce these movements would be most advantageous in rapid fire events, where a quick re-acquisition of the target is of prime importance.

Superstring,
I have a compensator on my Morini 162 EI short AP and am amazed how little the pistol moves after the shot. It really helps me concentrate on the sight picture to call the shot.

I have had other "inexperienced" people shoot my pistol and that muzzle is all over the place when the pellet leaves the barrel. I feel the comp allows me to see an error easier than without one. I'm thinking of "comping" my Hammerli 162 to see what I can learn.
Ben

Ben,
It is my understanding that the primary purpose of a muzzle compensator on an AP is to improve pellet flight by venting gases away from the pellet as it exits the barrel. I never observe any movement of the front sight on a properly executed shot whether the gun is uncompensated (IZH46), muzzle compensated (LP1) or has a compensator, ported barrel, and moving bolt (LP10/P44).

The idea of incorporating a counter moving bolt into a free pistol is interesting, but not sure how you could incorporate it into a typical falling block action.

Fred

ronpistolero wrote:Does this mean that if there was a blow back design for free pistol shooting, it would be more "forgiving", score-wise for the average shooter?

Ron

Nope!
All things being equal the amount of muzzle flip will be the same - the difference for 50m pistol is that there is no requirement for the centre of the bore to be above the web of the hand. A 50m pistol can be made to flip down if the barrel is lowered far enough in relation to the hand...

Spencer

I believe Webley made an 'auto-unloading' target pistol, which was a blow-back action, but which did not auto-load, so it's been done. I've never really understood why the idea hasn't been resurrected for free pistol use, because of its apparent advantages.

Spencer is right in that, in principle, the relationship of the barrel line to the hand/wrist can be made so that there will be no muzzle flip, in a locked-breech pistol, but, for perfection, this would have to be adjustable for each hand and possibly from day to day or shot to shot. However, the muzzle flip of a blow-back pistol occurs when the bullet is out of the barrel. and is generated by the slide hitting its stop, not the bullet acceleration. Muzzle blast will also contribute. So it's not the same.

Some of the basic physics are correct, but there are a few bits missing.
In the Auto, the case does not move in the chamber at the same time as the bullet. The expanding gasses act in all directions, and the case swells forcing it to bind with the chamber wall, the case does not move until the pressure drops sufficently to release the wall friction, then the case will move back with residual pressure.
Usually after the bullet has left the barrel and allowed gas escape (correct for all blowback pistols up to all .32 and a few .38's). Larger calibre pistols use locking rings to lock the chamber until the pressure drops/case starts to move and unlock the barrel either by cam or link.(simplified).
Also there are two parts to the recoil, one is the acceleration of the bullet to its escape velocity. But a greater part of the felt recoil is the gas escape from the barrel after the bullet has left.
To prove this, try the same bullet, loaded to the same velocity but using different burn rate powders. The fast powders have a short sharp crack in feel, and the slower powders have a much bigger, softer push.

Shooting Kiwi wrote:I believe Webley made an 'auto-unloading' target pistol, which was a blow-back action, but which did not auto-load, so it's been done. I've never really understood why the idea hasn't been resurrected for free pistol use, because of its apparent advantages.

Spencer wrote:

ronpistolero wrote:Does this mean that if there was a blow back design for free pistol shooting, it would be more "forgiving", score-wise for the average shooter?

Ron

Nope!
All things being equal the amount of muzzle flip will be the same - the difference for 50m pistol is that there is no requirement for the centre of the bore to be above the web of the hand. A 50m pistol can be made to flip down if the barrel is lowered far enough in relation to the hand...

Spencer

About blow back free pistols: the movement of the breech also participate to the recoil since it is a moving mass (much heavier than the bullet) and modifies the balance of the pistol. Thtat's why for RF pistol the trend is to reduce the mass of the breech as much as possible.

Lowering the barrel with respect to the hand in theory helps but not in practice since it is done at the expense of increasing the distance between the hand and the chamber.

When the barrel is (slightly) above the hand, the chamber can be very close to the hand = just above it. This is what is done in the Hammerli, TOZ, Morini free pistols designs.

When the barrel is moved down in line with the arm/hand, since there must be space for the trigger => the chamber must be moved forward = much farter away from the hand, this is the Steyr FP design.

Experience has shown that the performances of the later design were not as good as expected. This is the reason of the lack of success of the Steyr FP.

jipe wrote:
When the barrel is (slightly) above the hand, the chamber can be very close to the hand = just above it. This is what is done in the Hammerli, TOZ, Morini free pistols designs.

When the barrel is moved down in line with the arm/hand, since there must be space for the trigger => the chamber must be moved forward = much farter away from the hand, this is the Steyr FP design.

Experience has shown that the performances of the later design were not as good as expected. This is the reason of the lack of success of the Steyr FP.

There is a photo at

http://www.shootingwiki.org/index.php?title=Steyr_FP


Julian

ausdiver99 wrote:Is recoil in the form of muzzle displacement from the original state noticed as the projectile leaves the barrel (or shortly after it does) i.e having no effect on the trajectory or is it progressively felt as the projectile accelerates down the barrel? Years ago a rifle shooter told me it was the latter but I am not so sure that I agree with him.

Ther is a write up at;

http://www.shootingwiki.org/index.php?t ... ing_Recoil


Julian

About blow back free pistols: the movement of the breech also participate to the recoil since it is a moving mass (much heavier than the bullet) and modifies the balance of the pistol. Thtat's why for RF pistol the trend is to reduce the mass of the breech as much as possible.

If the case and slide are free to move, and for as long as this is the case, (and I take the point about gas pressure on the case adding to case-to-chamber friction), because momentum is conserved, the centre of gravity of the bullet - slide system (those masses moving in opposite directions, propelled by the same force) remains static. Perhaps counter-intuitive.

I think slide mass reduction is more to increase speed of cycling.

A couple of things:

Firstly, if you build a free pistol in which the chamber "blew open" on firing I would expect a significant reduction of accuracy due to the fact that any slight variations in ammunition pressure would be exagerated. The gripping effect on the chamber wall of a .22lr case is insignificant, that combined with the longer barrel typically used for a free pistol would require quite some mass in the "bolt" to delay the blow back. And as previously menetioned the movement of this mass would disturb the pistol as much if not more than normal recoil with no moving parts.

Secondly, the Steyr FP was a failure more due to the fact that it had a bad trigger mechanism and a awkward loading preceedure rather that the distance from the hand to the breech. I think it was also a bit "out there" for the market at which it was aimed.

Shooting Kiwi wrote:If the case and slide are free to move, and for as long as this is the case, (and I take the point about gas pressure on the case adding to case-to-chamber friction), because momentum is conserved, the centre of gravity of the bullet - slide system (those masses moving in opposite directions, propelled by the same force) remains static. Perhaps counter-intuitive.

Until the slide reaches the end of it's travel...