POI shifts 3" with American Eagle .223?

[flinch_of_gt]

This one confused the heck out of me. I've got a pre-ban Bushmaster XM15E2S A1, 11.5" bbl. There's a Tasco Pro-Point mounted on a B-Square see-through carry handle mount.

With Winchester Q3131A and PMC 223A (both 55 grain FMJ), the point of impact at 50 yards is the same as my POA..

Now, with Federal American Eagle 55 grain FMJ, the POI is three inches higher than my POA. I checked the mount and rings for looseness; didn't find any. I suspect that something has shifted in the scope, since I find it hard to believe that switching a brand of ammo would cause such a drastic change.

Any ideas?

 

[Fatelvis]

Try shooting the Win. stuff again, and see if anything did move. 3" is alot, considering they both use the same bullet weight, and are both loaded to Nato spec velocities, (or damn close). Let us know how it works out.

 

[stinger]

My Mosin will do that at 25 yards with several different kinds of ammo. Guns are funny like that.


Stinger

 

[C.R.Sam]

Could be normal.
Or could be something shifted.
Not unusual.

Sam

 

[mcole]

yeh, this is pretty typical. as long as the movement is up the centerline of the target, it is just the ammunition change. my experience is that if the point of impact moves up, it is a "hotter" cartridge ( but, there could be other reasons).
last fall i was fooling around at my gun club (no one else was out there) shooting my '06 at 25 yds. started out with wally world remington and winchesters using small bore pistol targets. with either, shots were absolute center of target. they shot some accelerators, some hornady light magnums and some the the top of the line federal 180 grain nosler partitions. aiming at the same point with each, the groups for each moved up the centerline on the target. one should really "sight in" for what they are typically going to shoot.
nevertheless, i would have thought the "q" cartridges would have been hotter than the american eagles. mcole

 

[Jamie Young]

I shot 500rd of AE threw My Mini 14 in the last year. I shot 300rd of SA ammo and THEY ARE NO WHERE NEAR THE SAME. AE is decent ammo but from what I've shot in the last 7yrs It's not as hot as what most Surplus ammo is. I have a 1000rds of Winchester 223 but haven't shot it yet. Maybe I'll fire some it tomorrow and report back.

 

[Mike Irwin]

Not uncommon at all.

Different cartridges, loaded with different components from different manufacturers, cause the barrel to vibrate in very different ways, which can cause large shifts in point of impact.

That's what the Browning Boss system is all about. It allows you to tune the barrel harmonics to the cartridge, rather than the other way around.

 

[Mark O]

It has to be the ammo

I shoot AK's using a red dot sight.I know I'll never achieve the accuracy of the .223 it's fun to shoot and more than adequate for a combat rifle.I try to stay away from Russian ammo and stick to S&B or SA.I buy by the case and with either one if I stick to the sme ammo for the next case I'll only have to slightly adjust(difference of POA of 3" isn't bad for an AK) my red dot.The Russian stuff is so inconsistint as to have as much as a 6 to 8" different POA with each case of the same ammo,and that can high,low,left,or to the right it varys so much.

 

[Al Thompson]

Mike's got it. I've had different handloads and brands make dramatic changes in both windage and elevation impacts.

For some reason, even some experianced riflemen don't realize that different lots of the same brand of ammo can have different POI/POA. It pays to get several boxes with the same lot number if you use factory stuff.

 

[4V50 Gary]

Common and that's why snipers keep in their rifle log the ammo's lot #.

 

[Jamie Young]

flinch_of_gt

I went to the range today and shot some Winchester Q3131A against American Eagle 55gr out of an AR XM15E2 and Mini 14. The AR shot 1.5inches higher, at 25yds, than the American Eagle. 3 inches high at 50yds is probable about right. Again, American Eagle is not loaded to what most Military 223 ammo is load to.