Does Changing AR Lowers Affect Zero

**Sgt.K** · December 25th, 2021, 02:17 PM

The question came up:

If I have multiple complete(d) AR uppers, can I shoot them all on the same lower to get them sighted in while waiting for their dedicated lowers to be finished? Assume all lowers from the same source and completed by the same person, if it matters.

I don't see why not, but I've never tried it before.

Thoughts?

**bogey1** · December 25th, 2021, 06:37 PM

I know for a fact that cleaning the barrel affects accuracy. Never tried what you mentioned.

**CycleTech** · December 25th, 2021, 07:18 PM

Originally Posted by Sgt.K

The question came up:

If I have multiple complete(d) AR uppers, can I shoot them all on the same lower to get them sighted in while waiting for their dedicated lowers to be finished? Assume all lowers from the same source and completed by the same person, if it matters.

I don't see why not, but I've never tried it before.

Thoughts?

It should not. You are zeroing the upper. that never changes when it goes on another lower.

**Rosco the Iroc** · December 25th, 2021, 08:26 PM

Only if you have a loose fit between them, but it shouldn't.

**jthrelf** · December 25th, 2021, 09:43 PM

Originally Posted by CycleTech

It should not. You are zeroing the upper. that never changes when it goes on another lower.

This.

You are zeroing the upper and sighting system(s) as one. The lower does not matter.

**Keith A** · December 27th, 2021, 05:17 AM

I would imagine its possible if the lower was severely out of spec, but I've never experienced it or heard of it happening.

**Sgt.K** · December 28th, 2021, 11:30 PM

Originally Posted by CycleTech

It should not. You are zeroing the upper. that never changes when it goes on another lower.

Originally Posted by jthrelf

You are zeroing the upper and sighting system(s) as one. The lower does not matter.

That was my general line of thinking.

Originally Posted by Rosco the Iroc

Only if you have a loose fit between them, but it shouldn't.

Yeah, the slop from pistol grip to handguard on my basic training M-16A1 was around 10 degrees from full twist one way to full twist the other - that sucker didn't have a tight joint anywhere. I still managed to hit 39 targets in 38 shots in one range session.