Zero change with different lots of popular ammo? M855, Mk262, etc.?

[DreadPirateMoyer]

Hey there everyone,

I was just wondering if any of you experience zero shifts with different lots of popular ammo types, like M855 and Mk262? I've noticed I sometimes get a 0.5" consistent zero change when using a different lot of M855, but I'm not completely sure if it's actually the different lot of ammo causing the shift or just the fact that I'm shooting on a different day and doing something differently than I was the day I zeroed.

If this is a common thing, how big of a shift does it usually lead to? Do you compensate for it? Do you rezero with every lot? Do you not care if it's a miniscule amount?

Additionally, have you noticed the same with precision-esque ammo like Mk262? I'm looking to make a large Black Hills purchase soon, and wasn't sure if I should be worried if my order comes with different lots (since a half-inch zero change would be a big proportional shift using Mk262).

Many thanks to those of you with more rounds down range than I've shot.

[T2C]

Ask Black Hills to package all of your ammunition from the same lot.

[markm]

Shit. Change of season alone will give you that much shift. Sticking with the same load is about as good as you can do. Then just check your zero periodically.

[mkmckinley]

You generally will see some zero shift from lot to lot but I'm not sure how noticeable it will be using green tip or some M193 clone. If you're talking a lightweight general purpose carbine I'd put rezeroing in the "not a bad idea and couldn't hurt" category unless I noticed some kind of major POI shift running drills. Generally with precision weapons you want to zero every time you get a new lot. When I reload 5.56 I try to do 1000 round batches and label/store that batch discreetly from the rest. An M249 ammo can will hold 28 loaded mags (quadruple basic load/840 rds) so I can load 100, pull the first hundred as "warm up" rounds to use as plinking fodder, and end up with at least 840 GTG rounds after culling the misfits to store in an ammo can.

[DreadPirateMoyer]

Thanks, fellas. Makes a lot of sense. I have a ton of different lots of M855 and have seen these 0.5" shifts almost every time I switch. I guess in the end, half an inch doesn't really matter (like you said, seasonal changes can do that in and of themselves), but it is kind of frustrating to have a stockpile of so many different lots and so many different potential zeroes.

I'll definitely ask Black Hills to package my ammo from the same lot when I make my order. That will help a lot.

[Keith E.]

Referring to your different lots you can record the impact change for each one and adjust accordingly when moving to a different lot. You would of course want to confirm zero at your first opportunity. IMHO, when purchasing bulk precision, it would be preferable to have all from the same lot.

Keith