What is the difference in velocity of a .22LR from bolt vs semi-auto?

[hminsky]

Does anyone know what the difference in muzzle velocity is of the same .22LR round shot from a bolt gun or a semi-auto?

It seems like there has to be some loss of energy from a .22 bullet due to the semi-auto cycling the action.

 

[seanc]

hmmm.. Interesting question..

My guess is that they'd be the same as the bolt is locked at the time of ignition.
Assuming the same bbl length, my guess is that the muzzle vel. would be the same, or within the deviation of the ammo specs.

If somebody has both a 10/22 and a 77/22 you could swap the barrel between the 2 (to eliminate the bbl as a variable) and chrono them.

 

[drumenigma]

You should get more velocity from the bolt action. In a semi auto some of the energy is expended cycling the action of the gun to chamber the next round resulting in a loss of some of the velocity. Typically it's not a significant amount of loss from the numbers I have seen.

 

[Mike-Mike]

I have an old .22 semi with the capability of locking the bolt closed.

 

[DickWanner]

You should get more velocity from the bolt action. In a semi auto some of the energy is expended cycling the action of the gun to chamber the next round resulting in a loss of some of the velocity. Typically it's not a significant amount of loss from the numbers I have seen.

Very true, gas operated recoil would soak up even more energy, but I don't think it's significant enough to be a concern. Though, by simple math/science/whatever it would make sense that a locked bolt design would yeild the higher MV.

 

[seanc]

You should get more velocity from the bolt action. In a semi auto some of the energy is expended cycling the action of the gun to chamber the next round resulting in a loss of some of the velocity. Typically it's not a significant amount of loss from the numbers I have seen.

Wouldn't the bullet have come free of the case before the case drives back the bolt?
My assumption would be that the case is expanding the bullet is free of the case prior to to the case driving back the bolt.

 

[dixidawg]

I would think it is negligible. I think the bullet is either long out of the barrel or so far down the barrel that any energy lost would not have gone into pushing the bullet faster:

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http://www.learnaboutguns.com/2008/12/02/springfield-xdm-firing-animation-video-clip/

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[45collector]

I have an old .22 semi with the capability of locking the bolt closed.

Me too. Mines a Springfield. So old, there's no serial #. Right on the barrel, it says something like: "22short, 22long, or 22LR. 22LR as semi-auto only."

I agree that you should get more velocity from a bolt action. No gasses being expended toward the rear gives more momentum.

 

[Mike-Mike]

Wouldn't the bullet have come free of the case before the case drives back the bolt?
My assumption would be that the case is expanding the bullet is free of the case prior to to the case driving back the bolt.

The projectile is still accelerating in the barrel from the burning gasses, If you use any of these gases before the bullet leaves the end of the barrel you are changing the energy.

 

[Mike-Mike]

Me too. Mines a Springfield. So old, there's no serial #. Right on the barrel, it says something like: "22short, 22long, or 22LR. 22LR as semi-auto only."

I agree that you should get more velocity from a bolt action. No gasses being expended toward the rear gives more momentum.

does the bolt stay open until you release the trigger.. like it has a delay?

 

[RKG]

You should get more velocity from the bolt action. In a semi auto some of the energy is expended cycling the action of the gun to chamber the next round resulting in a loss of some of the velocity. Typically it's not a significant amount of loss from the numbers I have seen.

None of the energy that is employed in a .22 autoloader (all of which are blowback operated) to cycle is energy that would otherwise be applied to propelling the bullet. As a result, all other things being equal, the muzzle velocity of the bolt and auto will be the same.

In theory, tapping some combustion gas pressure in a gas-operated, locked breach autoloader might be expected to have some negative influence on muzzle velocity. In reality, I'm pretty sure the effect is smaller than the variations you're likely to find in bore diameter and other factors, so that comparing a bolt gun and an autoloader would not permit one to see the difference attributable to gas tapping.

 

[vellnueve]

negligible

+1

 

[xring]

Not enough to matter.

 

[45collector]

does the bolt stay open until you release the trigger.. like it has a delay?

Yes it does. Pretty strange, I'd never seen a rifle that worked like that.

 

[Jose]

It seems like there has to be some loss of energy from a .22 bullet due to the semi-auto cycling the action.

There may be, but all else being equal (ammo choice and barrel length) I bet the difference between the two is so small that it gets lost in the normal variation of velocity from round to round.

 

[Jose]

None of the energy that is employed in a .22 autoloader (all of which are blowback operated) to cycle is energy that would otherwise be applied to propelling the bullet. As a result, all other things being equal, the muzzle velocity of the bolt and auto will be the same.

In theory, tapping some combustion gas pressure in a gas-operated, locked breach autoloader might be expected to have some negative influence on muzzle velocity. In reality, I'm pretty sure the effect is smaller than the variations you're likely to find in bore diameter and other factors, so that comparing a bolt gun and an autoloader would not permit one to see the difference attributable to gas tapping.

It is possible to lose some of the propellant gas as the bolt unlocks in a semi auto if the bullet is still in the barrel. I know, I know, the effect is likely negligible.

 

[jhrosier]

My theory is that there is a finite amount of energy in the direction opposite the motion of the bullet. It can all go to recoil in a bolt gun, or be expended in heat generated by friction when moving the breech block and in heat by compressing the recoil and striker springs, with the remainder becoming recoil in an autoloader. Except for the heat losses due to friction and spring compression, there is no energy lost. Only in a case where the breech opens early enough to release high pressure gas into the action would there be any change in the velocity. The delay in opening the breech of a typical .22 rimfire gun is generally enough to prevent the loss of high pressure gases.

Since the total energy expended rearwards does not change with a change in action type, the amount of energy available to move the bullet will also not change.

When calculating the energy expended in moving the bullet, remember to allow for losses due to friction between the bullet and barrel.

Further, a typical .22 rimfire load has achieved its' maximum velocity usually in the first 12 to 14 inches of bullet travel, which would occur long before the breech block has moved enough to allow the escape of high pressure gasses.

While all of this applies to standard or conventional types of .22 rimfire ammo, some of the modern high-performance ammo, such as CCI Stingers, probably push the velocity up mainly by the use of slower burning powders and slightly higher pressures. The basic principles still apply even though the burning time is slightly longer and pressures are a little higher.

Jack

 

[boomerang]

Bullet would be out of the barrel before the brass contracts.

 

[RKG]

It is possible to lose some of the propellant gas as the bolt unlocks in a semi auto if the bullet is still in the barrel. I know, I know, the effect is likely negligible.

If the bolt "unlocked" while the bullet was still in the barrel, you'd have quite a fireworks show!

As a general matter, chamber pressure has to reduce to near or below 10 psig before the action begins to move the bolt out of battery.