XM193 worse with barrel temp?

[ArgentFix]

Last fall I semi-panic-bought a Sport II, slapped on a Romeo5 and zeroed at 50yd with cheap Wal-Mart Federal .223 (#BP223BL ). Last group after zeroing:



Fine. Then I continued with some XM193 headstamped "FC 17" from (I think) a Natchez loose bulk case:



Something was wrong with me or the gun or the ammo so I quit for the day. A couple weeks later I shot at an indoor 25yd range (hence the low POI). I alternated between the #BP223BL (right) and XM193 (left) going from bottom to top, every 10 rounds. My groups with the .223 tightened while my XM193 groups slightly expanded:



Is it possible XM193 (or at least my lot) gets less precise with barrel temperature while other ammo does not?

[HCM]

Last fall I semi-panic-bought a Sport II, slapped on a Romeo5 and zeroed at 50yd with cheap Wal-Mart Federal .223 (#BP223BL ). Last group after zeroing:



Fine. Then I continued with some XM193 headstamped "FC 17" from (I think) a Natchez loose bulk case:



Something was wrong with me or the gun or the ammo so I quit for the day. A couple weeks later I shot at an indoor 25yd range (hence the low POI). I alternated between the #BP223BL (right) and XM193 (left) going from bottom to top, every 10 rounds. My groups with the .223 tightened while my XM193 groups slightly expanded:



Is it possible XM193 (or at least my lot) gets less precise with barrel temperature while other ammo does not?

No. It's your bulk pack XM193. I've had similar issues with the Speer/Federal Black Friday Bulk pack .223 and 9mm.

[alamo5000]

I don't think it has anything at all to do with heat at least for the most part. I think that ammo just isn't the best choice for your gun.

If you were having temperature issues it would be something else entirely. If there are stresses inside the metal that were created when the barrel was manufactured those will often reveal themselves with the addition of heat. Same thing can be true if you simply have a poorly manufactured barrel. So yes the accuracy of a gun can easily degrade really bad with the addition of heat (if that were the problem).

I however do not think that has anything to do with it based on what I am seeing here and what you are saying.

[ViniVidivici]

Different guns just like different ammo sometimes, but M193 is not by any standard "match grade". That"s all it is.

[theJanitor]

... but M193 is not by any standard "match grade". That"s all it is.

And XM are the rejects.

[ArgentFix]

M193 is not by any standard "match grade". That"s all it is.

And XM are the rejects.

Understood. I guess I was surprised at the difference between "XM tier" and "Wal-Mart tier" Federal 5.56/.223, the latter being several-MOA superior in my lots and gun.

It's 2021. Weirder shit has happened.

[fatdog]

Hot barrels grow group sizes, any ammo. In some less expensive barrels the heat can shift POI, center of the growing group, with any ammo. As stated by others, XM193 is not premium ammo, some lots of it got to be "X" lots because they could not meet the group/accuracy standards from the test barrels at Lake City.

[M2CattleCo]

I love it when I get a case/lot of ammo that won’t group.

Now I have an excuse to do hoser things!