Recoil and POI

[All~American]

Hopefully this doesn’t start WW3 but I’ve accumulated a question concerning the affects that recoil has on your POI. While doing some load development with my AR chambered in 5.56, I had a few shots out of my vise where I wasn’t properly shouldering my rifle (it was an awkward position). The load turned out to be a bust but I began to wonder if excessive recoil from improperly stabilizing my rifle was causing major POI shifts. To simplify, theoretically: if I were to put my rifle in a gun vise without personally holding it at all, and I simply pulled the trigger using my finger only (which would essentially send the rifle jarring backwards), does the recoil from combustion happen fast enough to affect the POI of the bullet? Or is that recoil completely after the fact of the bullet leaving the barrel not changing POI at all?

 

[MarkCO]

Yes, how you hold the rifle will affect POI, even velocity. Heavier rifles, manually operated rifles, faster cartridges all mitigate that to some degree.

 

[All~American]

I was leaning towards what you said after giving it some thought, it’s good to hear some reassurance. I appreciate it

 

[A&8's]

You can most definitely 'beat the bullet' out of the barrel. In the words of @lowlight "Press, Break, Freeze."

 

[1moaoff]

Not to sound like a downer.... but load development in a vice or sled is not highly thought of in many circles.

For exactly the reasons you stated, how you engage the rifle will affect it.

As an aside what is possible from a machine rest rarely transfers to actual shooting in my opinion.

 

[All~American]

Not to sound like a downer.... but load development in a vice or sled is not highly thought of in many circles.

For exactly the reasons you stated, how you engage the rifle will affect it.

As an aside what is possible from a machine rest rarely transfers to actual shooting in my opinion.

I have since heard this a lot and have decided to reform from shooting in a vice, it is very stable but far too awkward and restrictive. As you said, it’s basically unrealistic

 

[Macht]

Mostly just echoing what others have said with a little more detail:
Only a small portion of the recoil occurs while the bullet is in the bore, but it is long enough to have an effect. Lots of variables come into play (cartridge, barrel length, firearm mass, etc), but in a free recoil scenario you would have roughly a tenth of an inch of rearward movement prior to bullet exit. If that movement is resisted the energy still has to go somewhere, and the degree/placement of resistance will ultimately change the barrel motion and POI.

 

[Baron23]

Managing recoil, along w trigger control, are my current two points of emphasis for improving my precision.

 

[All~American]

Mostly just echoing what others have said with a little more detail:
Only a small portion of the recoil occurs while the bullet is in the bore, but it is long enough to have an effect. Lots of variables come into play (cartridge, barrel length, firearm mass, etc), but in a free recoil scenario you would have roughly a tenth of an inch of rearward movement prior to bullet exit. If that movement is resisted the energy still has to go somewhere, and the degree/placement of resistance will ultimately change the barrel motion and POI.

Thank you for the more detailed explanation on this! Would it be correct to assume that the majority of the recoil happens after the bullet leaves the barrel, given that it is a semi auto and the BCG doesn’t completely cycle till the bullet is gone? Obviously not taking away from the importance of still managing your recoil though.

 

[Bigjake83]

Hopefully this doesn’t start WW3 but I’ve accumulated a question concerning the affects that recoil has on your POI. While doing some load development with my AR chambered in 5.56, I had a few shots out of my vise where I wasn’t properly shouldering my rifle (it was an awkward position). The load turned out to be a bust but I began to wonder if excessive recoil from improperly stabilizing my rifle was causing major POI shifts. To simplify, theoretically: if I were to put my rifle in a gun vise without personally holding it at all, and I simply pulled the trigger using my finger only (which would essentially send the rifle jarring backwards), does the recoil from combustion happen fast enough to affect the POI of the bullet? Or is that recoil completely after the fact of the bullet leaving the barrel not changing POI at all?

Mark Larue, is that you??
Always sneaking on the Hide for marksmanship advice.

 

[Macht]

Thank you for the more detailed explanation on this! Would it be correct to assume that the majority of the recoil happens after the bullet leaves the barrel, given that it is a semi auto and the BCG doesn’t completely cycle till the bullet is gone? Obviously not taking away from the importance of still managing your recoil though.

Yes, most of the recoil and barrel movement happens after the bullet has left the barrel. I'm not an expert on gas systems, but from what I've read in old Army papers the BCG hasn't even really begun to unlock at the time the bullet leaves the barrel, let alone cycle. For context, from ignition to bullet exit will take 1-2 ms (depending on load and barrel length) whereas the full cycling of the action in an AR takes more like 50-60ms.

 

[All~American]

Mark Larue, is that you??
Always sneaking on the Hide for marksmanship advice.

Shucks, foiled again

 

[All~American]

Yes, most of the recoil and barrel movement happens after the bullet has left the barrel. I'm not an expert on gas systems, but from what I've read in old Army papers the BCG hasn't even really begun to unlock at the time the bullet leaves the barrel, let alone cycle. For context, from ignition to bullet exit will take 1-2 ms (depending on load and barrel length) whereas the full cycling of the action in an AR takes more like 50-60ms.

Great to know thanks again man.

 

[Baron23]

Would it be correct to assume that the majority of the recoil happens after the bullet leaves the barrel

Does it matter.....goal is to control recoil, stay in position, stay on the trigger through the shot to the end. Right?

 

[MarkCO]

Yes, most of the recoil and barrel movement happens after the bullet has left the barrel. I'm not an expert on gas systems, but from what I've read in old Army papers the BCG hasn't even really begun to unlock at the time the bullet leaves the barrel, let alone cycle. For context, from ignition to bullet exit will take 1-2 ms (depending on load and barrel length) whereas the full cycling of the action in an AR takes more like 50-60ms.

Direct Impingement systems (AR15 DI) have 4 recoil impulses, which is why they are harder (not impossible) to get to the accuracy level of bolt guns that have one. Yes, most of that movement happens after the bullet has cleared the barrel. And yes, most of that is affecting the fundamentals of follow through and reducing consistency of follow up rounds. But, the bullet, right as it clears the barrel, and for at least a small amount of time, "It's flying supersonically backwards man!". While not technically correct, that old quote from one of my ballistics professors does have some merit. The expanding gases continue to act on the base of the bullet after it has left the barrel. If the barrel is shifted off of it's original axis in that time, it can (and does) impart yaw to the bullet. In the "traditional" overgassed AR, it is possible to unlock the bolt while the bullet is still in the barrel and or shift that expanding gas column due to that 2nd complex recoil impulse. The longer the dwell time (after the bullet passes the gas port but before it has left the barrel) the more chance you have of actual mechanical motion related to the system. Unlocking the bolt on an AR results in both rear thrust and torque. The third impulse, when the BCG reaches the end of rear travel, and the 4th, chambering another round, won't affect the fired bullet at all, just contributes to altering your position and relationship to the gun. The softer the hold, the more the torque component will be on that 2nd recoil impulse.

 

[GUNNER10]

Basically everything from position to weather effects POI. The more consistent you are with the fundamentals, the more accurate your will find yourself

 

[Ravenworks]

☝ this ☝
To go with the post above you need to think about feeling the rifles impulses and using them.


The device attached to the end of your barrel will make a huge difference.
You will develop a rhythm with the rifle and you'll know you have it because it will feel natural.

 

[All~American]

Does it matter.....goal is to control recoil, stay in position, stay on the trigger through the shot to the end. Right?

Oh no I agree with you, it’s just become more a curious question of its physics than anything else. I like to know what works but also why it works beyond following formulas

 

[Baron23]

I like to know what works but also why it works beyond following formulas

I'm very much the same way....deep dive first until I understand completely, then pull back to a practical level of detail.

Best of luck.

 

[All~American]

I'm very much the same way....deep dive first until I understand completely, then pull back to a practical level of detail.

Best of luck.

Exactly, thanks a ton for the insight

 

[Macht]

But, the bullet, right as it clears the barrel, and for at least a small amount of time, "It's flying supersonically backwards man!". While not technically correct, that old quote from one of my ballistics professors does have some merit. The expanding gases continue to act on the base of the bullet after it has left the barrel. If the barrel is shifted off of it's original axis in that time, it can (and does) impart yaw to the bullet.

That's a good point on the intermediate ballistics period. I've never heard that phrasing before, but it really does convey the idea well.