How critical is the Upper receiver brand on accuracy for a DPMS pattern AR-10?

[ReaperDriver]

Hi all,

Quick question as I'm in a dilemma....... I have bought all the parts to build a "no compromise" precision AR-10 6.5 upper for PRS matches and Long range steel fun from a top tier company. The plan was to assemble the upper keeping all the parts - upper, barrel, bolt, BCG, FA, pins, etc from the same manufacturer. The plan was to mate this to an existing GAP-10 lower that I have from a Gen 1 GAP rifle where I sold the .308 complete upper off of in order to do this build. I have everything now except the stripped Upper receiver - which has been on backorder since Oct 2020, with no ETA in sight. So I'm considering cnx'ing the stripped upper order and going with the next best maker. Something like Aero, Seekins, etc. I was trying to avoid building a Frankenstein gun with various parts given that there is far less standardization of parts in AR-10s compared to AR-15s. But, I'm becoming impatient with waiting on that one part to complete the build and start shooting.

So Q1 is: How critical is the stripped upper on real life accuracy if the barrel, bolt, BCG, Gas block, etc are matched together?

Q2: How critical is the upper to lower mating on real observed accuracy assuming they fit together and function OK without modification? Would I be better off getting a matched upper/lower set to get a better fit? i can always sell off the GAP lower if a matched set makes more sense.

My (admittedly limited) understanding is that the barrel and a properly headspaced matched bolt was the most critical link for pure accuracy in a Semi and the receivers themselves were less critical as long as they are not "sloppy" fit.

Any thoughts and/or advice on how best to proceed would be greatly appreciated.

 

[bfoosh006]

http://bulletin.accurateshooter.com...-to-build-a-truly-accurate-ar-platform-rifle/

https://www.gunsandammo.com/editorial/accurize-your-ar-15/247749

I believe a snug fit upper to lower fit certainly makes it easier for you to wield the firearm more consistently. I also view a good fit to be much like bedding a bolt action to its stock.

So to me it most certainly matters. I believe it to be one of the more critical factors. I would certainly seek a good fit between the upper and lower.

There will be some that say it doesn't matter... and will quote the USGI test concerning the loose upper to lower subject from the Vietnam War Era test. But , few have read that actual test.. and the US Army test parameters considered up to 7 MOA still acceptable for a combat M16.

So to me that test is a mute point ... ( unless they were to redo the test today )

Just my 2 cents.

 

[Near miss]

I agree with that. But I have no data other than my own rifle, they lock very tight.

But there are also those adapters that remove the slack between them. I have heard they have mostly positive effect, which kind of proves the point?

I do not see other way a lower could deterioriate accuracy, apart from unergonomic / badly fitting / loose stock.

 

[snarkscarbine]

Upper trueness/barrel extension fit is more important by a long shot than upper/lower fit, but upper/lower fit does help. I've had cheap guns where there was enough slop between the receivers that the upper could wiggle independently of the lower, which obviously isn't great for shot-to-shot consistency.