What makes a AP "kick"?

[toddinjax]

I shot a Steyr LP1 at my club last night an it had a pretty pronounced kick. Would this be most likely caused by a too high velocity setting or something else at (foul) play? I am most used to a IZH 46m so any pcp seems pretty hot by anecdotal comparison.

[GOVTMODEL]

See Newton's third law.

[brent375hh]

Compared the the IZH, it is either:
The LP1 is a lighter gun
The LP1 is shooting a higher velocity.

[Gwhite]

Compared the the IZH, it is either:
The LP1 is a lighter gun
The LP1 is shooting a higher velocity.

Probably both.

[Rover]

Don't worry about it until the gun rears like a bull prod to a stallion's taint.

The pellet is gone by then anyway.

[ojh]

The pellet is gone by then anyway.

Rover, I sincerely hope that you are not a heretic.

The gun starts to move backward at the very same moment as the pellet and air start to move forward. You know, conservation of momentum and all that stuff.

[dulcmr-man]

If I figured it correctly the pellet leaves the barrel in about 18 milliseconds, so there will be SOME barrel rise in the time, but not much.

[Grippy]

Would be interesting to do the math on this but I'd wager that while the acceleration starts the moment the pellet starts moving most of the movement happens after it is already out.

[-TT-]

It doesn't much matter if the barrel kicks in single-shot discipline, as long as it kicks the same every time. A skilled shooter will hold consistently, and adjust the sights slightly downward to hit the desired POI. Off a rest, the gun may hit low, but where it counts, the rise is managed out. Of course, the devil's in those details... :)

I think another aspect of the kick is the size of the air charge, and the speed of the valve. A large charge of air will present more stored potential, and a fast valve a more rapid release, which will magnify the recoil more than simply the mass of the accelerating pellet.

[divingin]

Would be interesting to do the math on this but I'd wager that while the acceleration starts the moment the pellet starts moving most of the movement happens after it is already out.

Physics would get pretty involved, I think. Figure on the pellet accelerating from 0 to 500ish fps within the barrel. 7 or 8 grains vs whatever the pistol weighs. Off-center acceleration on the mass of the pistol. Ugly.

I'd guess the pistol will move a bit during the barrel-time of the pellet, but agree most will occur after it's left the muzzle.

[Green_Canoe]

Would be interesting to do the math on this but I'd wager that while the acceleration starts the moment the pellet starts moving most of the movement happens after it is already out.

Physics would get pretty involved, I think. Figure on the pellet accelerating from 0 to 500ish fps within the barrel. 7 or 8 grains vs whatever the pistol weighs. Off-center acceleration on the mass of the pistol. Ugly.

I'd guess the pistol will move a bit during the barrel-time of the pellet, but agree most will occur after it's left the muzzle.

The basic physics aren't too involved until you bring in the dampening of movement due to the hand holding the gun.

There is no time factor in the conservation of momentum. As soon as the pellet moves the gun moves. Of course, the gun moves much more slowly than the pellet. Displacement is related to time. The displacement of the gun will be far less for a given time period than the pellet due to the difference in velocity between the two.

[Grippy]

But not the entire work is applied at once though. The force on the gun is the reverse of the force on the pellet which in turn is directly proportional to the pressure acting on the pellet. So as the pellet moves down the barrel the pressure drops and so does the force. And the interesting question is how much is the gun displaced before the pellet leaves the barrel.

[Rover]

There has been some pretty involved reasoning in this thread. Good to see that there are some "sharp" ones on TT.

While this has been some useful information, I'm sure the original poster would be most successful if he would just "hold his mouth right".

[High Left]

There's also the 'jet' effect of the air leaving the bore after the pellet unstops it. Ports in the barrel change all that as well.

And being an older model, I don't think it has any sort of compensator in it like the new ones. My Fwub makes a pretty good pop, but I don't notice any recoil at all. It has a compensator in the bolt, and ports in the barrel.

[Oldbear]

And yet it kicks!
There must be some additonal force causing the upward kick. Perhaps the impact of the hammer on the release valve?
Or is it all flinch and trigger jerk?

[BobGee]

I’m sure there's a joke in there somewhere about jerks.

Bob

[william]

Come on, guys. How much simpler can it be? When the gas is released into the chamber, as it expands it pushes with equal force in all directions. Movement is only possible longitudinally.
1) In one direction the pellet is pushed toward the muzzle.
2) In the opposite direction the pistol is pushed toward the shooter.

#2 accounts for the felt recoil. Muzzle flip results from nothing more than the fact that all that business is going on above the wrist which acts as a fulcrum. I feel pretty confident that if you could hold the pistol on the axis of your wrist/forearm there would be no muzzle flip at all. And if you held it below, the muzzle would be perfectly happy to move downward.

As for "jerks," this jerk can deflect the muzzle in any random direction and usually at the worst possible time.

[High Left]

Every force ... equal and opposite ...

Figure the weight of the pellet, and how fast you want it to go in what distance. Add a spring loaded weight in the bolt, pushed back by the same blast of air.

The distance it needs to move is roughly pellet weight x acceleration / compensator weight. Or something roughly like that.

Same goes for the old recoiless springers, but add the weight of the piston and it's speed to the pellet's. I don't notice mine jumping at all, just see the slide come back a bit before I blink.

[crankythunder]

Ok guys, here is a way to measure if recoil effects bullet impact. Well, not exact but pretty close.

Make sure the pistol is zeroed dead nutz.

Get a 36 inch dowell or a steel or aluminum rod that fits inside the barrel of your pistol. Insert it such that the majority is sticking out the front of the pistol.


Place the pistol in a vice.

Now take a 4 foot carpenters level and set it on top of the front sight and on top of the blades of the rear sight. take your time and balance it so it stays put.

Stand back and take a look.

let me know if the dowel in the barrel is parallel to the level on top.

Tell me what you see.

[Grippy]

The Idea being that the rod should point slightly downwards in "anticipation" of the kick?
To use that information you'd also have to consider how much the bullet drops though. Which for 150m/s over 10m should be order of magnitude 2cm.