AR accuracy, 1 lower, multiple upper

[WestKentucky]

I just put a Cheapo magnified scope on my rifle, and I noticed a fair amount of slop in the upper/lower fit. If I was going to have a dedicated upper/lower mate I could easily get a lot of this slop taken up and make the fit solid. My plan however is to have 1 lower and at least 2 uppers if not 4 or 5. So how do I go about fitting these parts so that they are secured nice and firm? I understand I will be fitting uppers to a common lower, but where should I be focussed? I know it's a noob question, but I haven't ever had a need to fit parts together in such manner. My only other multi-caliber gun is a contender and my barrels all lock up nice and tight so no issues there.

 

[MaterDei]

Some ARs deal with the slop between the upper and the lower. I have a Sig M400, for example, and the slop between the upper and lower is minimized with a spring operated tensioner in the lower. Here is a picture of that.



There are ways that you can deal with this slop yourself, google it, you will find plenty of advice.

With that said, the slop between the upper and lower should not be a big concern. Your scope is mounted to the upper and any slop between the upper and lower will not impact the zero of your scope to the upper. Same goes for any other uppers that you put on the lower.

Hope this makes sense and that it helps.

 

[Jackal]

Loose upper/lower fit is annoying, but it doesnt really affect anything. A 25cent o-ring around the front takedown lug fixes all the slop.

 

[Lloyd Smale]

I agree with jackle. I have a very accurate (1/2 minute) heavy barreled ar. Buddy and I fooled around one day and swapped the upper onto 4 different lowers and it didn't change a thing. other them maybe a bit of consistency because a couple of the lowers had heavy trigger pulls but when we did our part they all still shot just as well.

 

[WardenWolf]

Everything that affects accuracy is in the upper receiver. The only way you could have problems is if it was REALLY loose, in which case it may shift under recoil before the bullet has left the barrel. It'd have to be unacceptably loose for that, though. Like visibly wobbling and rattling.