Anyone ever seen much accuracy difference in switching just a lower ? going to run some experiments the next week or so.

I have a 6.5 Grendel as well as 2 556 uppers and they all get time on the same lower.

It has a Magpul stock and the lower is made by Aero all uppers are Aero as well.

I have not seen any difference all uppers lock up tight.

No.

Please do post your results.
I was just thinking about that this morning as I looked at some holes in som paper and realized I knew which upper, but had NO idea which lower!
Will be interesting to see you results.
I know it sure seemed to with the Contender!

I just completed 2 pistol lowers. Switch my uppers back and forth with no change in accuracy.
Certainly not a scientific sample but gives me confidence when I grab one.

The only difference in accuracy you'll notice from switching lowers is one that affects your accuracy with trigger pull issues.

If you have a chit trigger on one, you may not be able to as accurate as the lower that has a great trigger.

I had one upper/lower pairing that was loose. Real loose. But it didn't affect accuracy either. That rattle trap shot well.

If the lowers and uppers are not bedded to each other there is a noticeable accuracy change.

That change came from me shoot a LOT of 10 shot test groups off the bags at 300 here at the house in Texas.

Bedded did 2 really clear things. It made the groups rounder and less overall dispersion from center. And in that process the groups ended up being about 1/10 of an inch tighter overall. That was a lot of averaging to get to that number. But they were always prettier groups.

SO for the average guy or gal doing average things you will never notice any difference.

I've been busy and not got around to amox permanent or it's been extremely windy. Why ask this question I had a Grendel upper Areo lower with a very nice trigger in it I never was completely happy with the accuracy of that upper. I bought a whole different up and stuck on it the accuracy is definitely better but it's still not as good as most of my stop 556 stuff. I mean my factory Colt out shoots it a long ways and Factory PSA out shoots it quite a bit. So I got to thank and I've always shut the Grendel uppers on that lower I was going to switch lowers and see if it changed anything I don't figure it really will either but I've been surprised before

Spend the money on a decent barrel for accuracy, don't worry about the lower, especially if you've already got a decent trigger in it.

Pretty much correct. At least for most uses of the ARs for sure.