I used to always be concerned that different ammunition would shoot to different POI in any given gun.  I finally had several different types of ammo on-hand so I tested out that theory at the range yesterday.  All stayed within the 2" diamond on a shoot-n-c target at 50 yards and within the 4" diamond on the same target at 100 yards.  Some were slightly higher or lower than others, but remained in the target area.  I was shooting off of an improvised rest (a towel draped over an ammo can) and was shooting a slightly modified Colt 6520 with 1.5x mini-ACOG.  I initially zeroed the rifle using Wolf 62 grain polymer coated before firing the rest for groups.  The ammo used was:
Federal XM193 55 grain
Wolf Polymer 55 grain
Wolf Polymer 62 grain
Black Hills 75 grain

I understand that for real accuracy testing I should have used a vice of some sort or at least a sandbag rest.  I think that my test was still applicable for my purposes for this rifle.  I also would have been able to better evaluate the shift in POI if I used a higher-power optic or a heavier barrel, but again I'm trying to stick with what I shoot.

Let's get this straight, you have XM193 and BH 75grn in your SHTF ammo stock, but your rifle is zeroed using the Wolf?

Do ya not know the difference between plinkin ammo and quality self-defense ammo?

FWIW, I think you need to re-read the Ammo Faq tacked to the top of the Ammunition Forum.

Mike

Thanks for the range report.  If it where me, I would of zeroed with the most plentiful shtf ammo.  In my case I zero with M855, and then I plink with AE 55gn stuff or the Wolf 62 gn stuff.  This way if I ever have to grab my mags (marked SHTF), I know that my zero will be right.

I'm glad to hear about your groups POI vs POA, Mine are about the same.  I do notice a little bigger variance when I switch from my 16" 1/7, to my 11.5" 1/7.

Quoted: Let's get this straight, you have XM193 and BH 75grn in your SHTF ammo stock, but your rifle is zeroed using the Wolf? Do ya not know the difference between plinkin ammo and quality self-defense ammo? FWIW, I think you need to re-read the Ammo Faq tacked to the top of the Ammunition Forum. Mike

Maybe you don't read so good.

The point of all this is that, errornet commandos like yourself aside, it doesn't functionally MATTER what you zero with.

I think if you had expanded your testing to other ammo it would have made a bigger difference. I had some older UMC and several other ammos that were quite different in the POI and POA.
Some as much as 5 to 6 inchs at 100 yard which is pretty dramatic to me since I like to know exactly where my shot will go. Yeah it may not make much of a difference at a man sized target standing facing you in the wide open but I don't expect to see someone often like that in a firefight since they would probably be using cover also.
JR

Quoted: I think if you had expanded your testing to other ammo it would have made a bigger difference. I had some older UMC and several other ammos that were quite different in the POI and POA. Some as much as 5 to 6 inchs at 100 yard which is pretty dramatic to me since I like to know exactly where my shot will go. Yeah it may not make much of a difference at a man sized target standing facing you in the wide open but I don't expect to see someone often like that in a firefight since they would probably be using cover also. JR

That's pretty interesting.  I only shot what I had on hand and what I would use for matches and training.  a 5-6" shift is pretty dramatic.  What were the projectile weights of the two loads that had the most shift?