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-   -   POA/POI affected by recoil spring? (http://www.firearmstalk.com/forums/f14/poa-poi-affected-recoil-spring-45773/)

Poink88 07-25-2011 05:51 PM

POA/POI affected by recoil spring?
 
If your semi-auto pistol is using an 18# recoil spring and you replace it with a 13# spring. Will it change your POA/POI? If yes, should you expect it to go higher or lower (if using same ammo)?

IGETEVEN 07-25-2011 06:19 PM

Quote:

Originally Posted by Poink88 (Post 549617)
If your semi-auto pistol is using an 18# recoil spring and you replace it with a 13# spring. Will it change your POA/POI? If yes, should you expect it to go higher or lower (if using same ammo)?

That can only be determined once the first few shots are fired and the caliber type, weight of original handgun and the ammo grain used. Adjustments for POA/POI may, or may not be needed.

JonM 07-25-2011 06:54 PM

It wont affect it. Newton still applies. The gun wont move or recoil until the bullet exits the muzzle. The force of the round going forward is equal to the rearward force until the equation changes as the bullet exits. The forward thrust is no longer there to offset the rearward force or recoil. So this makes weight of spring a moot issue in terms of affecting poapoi

You can see it in action on any highspeed camera shot of a gun going off

Poink88 07-25-2011 06:58 PM

Quote:

Originally Posted by JonM (Post 549653)
It wont affect it. Newton still applies. The gun wont move or recoil until the bullet exits the muzzle. The force of the round going forward is equal to the rearward force until the equation changes as the bullet exits. The forward thrust is no longer there to offset the rearward force or recoil. So this makes weight of spring a moot issue in terms of affecting poapoi

Hmmm. I agree that Newton's law applies but for me, it starts at primer ignition not when the bullet exits the barrel. As the bullet moves forward, the slide moves backward simultaneously.

The reason heavier bullets hit higher than lighter bullets (early part of trajectory) is because they stay in the barrel longer (travels slower).

JonM 07-25-2011 07:05 PM

Quote:

Originally Posted by Poink88 (Post 549658)
Hmmm. I agree that Newton's law applies but for me, it starts at primer ignition not when the bullet exits the barrel. As the bullet moves forward, the slide moves backward simultaneously.

The reason heavier bullets hit higher than lighter bullets (early part of trajectory) is because they stay in the barrel longer (travels slower).

Yes but the force forward still equals rear. Equal and opposite. Recoil doesnt start till the bullet is gone. Weight of bullet and external ballistics is different than internal ballistics. Same exact bullet charge primer etc with only a spring change poapoi wont change.

Poink88 07-25-2011 07:08 PM

The force is equal but will the speed of the slide recoil not change with a lighter spring? Thus, won't it affect how fast the barrel tilts upward as well as the pistol itself?

JonM 07-25-2011 10:15 PM

Quote:

Originally Posted by Poink88 (Post 549664)
The force is equal but will the speed of the slide recoil not change with a lighter spring? Thus, won't it affect how fast the barrel tilts upward as well as the pistol itself?

yes but that has no effect on poa/poi of the bullet itself. the spring and slide dont start moving until after the bullet is gone. this is true of revolvers too.

this demonstrates it the best. the flash is when the bullet has left the barrel and recoil starts.

http://youtu.be/s5pVya7eask?t=23s

Poink88 07-26-2011 02:00 PM

Quote:

Originally Posted by JonM (Post 549731)
yes but that has no effect on poa/poi of the bullet itself. the spring and slide dont start moving until after the bullet is gone.

Jon, I would respectfully disagree.

The slide and spring definitely will not move as fast as the bullet but I believe they start moving as soon as you had an ignition. Again, this is the reason why heavier (slower) bullets tend to hit higher than lighter (faster) bullet. As fast as they fly out, they are still affected by the barrel movement/recoil.

Of course the entire pistol also start the recoil process at the same time and depending on the grip, POI may also change.

Just my personal beliefs/understanding which may be wrong.

Poink88 07-26-2011 02:03 PM

Quote:

Originally Posted by IGETEVEN (Post 549633)
That can only be determined once the first few shots are fired and the caliber type, weight of original handgun and the ammo grain used. Adjustments for POA/POI may, or may not be needed.

Much as I wanted a more definitive answer, I guess this is the simplest way to go through this. Thanks!

IGETEVEN 07-26-2011 02:12 PM

Quote:

Originally Posted by Poink88 (Post 550148)
Much as I wanted a more definitive answer, I guess this is the simplest way to go through this. Thanks!

Ya just gotta go with the flow man. Life always requires them little adjustments to maintain one's overall personal proficiency. ;)


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