I have cowitnessed an LMT 10.5 upper along with my RRA lower. The finish matches really good but there is just a tad bit of “play” between the two. My question is will this hinder accuracy and if so, how do you fix it. I hear that the wedges arent all that great. Thanks.
Nope.
What S-1 said, nope, but you can spend $6.00 on a small piece of plastic to wedge the 2 pieces together. 
Speaking from a couple years of shooting national match AR service rifles, No. Upper /lower play has no affect on accuracy, but can affect your confidence in your rifle. Accu wedge is worth the piece of mind and no one really likes it when there upper flops around. My basic training rifle was atrocious, but grouped just fine. I have also seen and used at camp perry, sliced bits of rubber sheet, folded cardboard, anything that puts upward pressure on the rear lug.
As stated, no. I have qualled expert on some really floppy M16A2’s. Unless your rifle is demonstrably inaccurate, I would just leave it alone.
Each time the weapon system cycles, the bolt carrier (which is part of the upper receiver) travels into the buffer tube (which is part of the lower receiver).
An accuwedge or any other item placed in the gap to tighten the fit may cause the bolt carrier to drag on the buffer tube. This may result in unnecessary wear on both parts and could also lead to a malfunction.
I see absolutely no reason to have an accuwedge in an AR particularly one for duty use that will get high round count.
However, I wish I was the guy that invented it ($6 for a $0.10 part).
The big drawback to accu wedges is that they significantly tighten the upper and lower receiver to the extent that it takes a punch to open the the 2 halves, a real inconvienience, when you need to scope out a problem. I haven’t used one in 2 years just for this reason.
Something that drives the two halves apart just seems wrong somehow. If I had to have them fit tighter, I’d go with the JP rifles solution:
http://www.jprifles.com/buy.php?item=JPTP-1
I tried the JP tensioning pin but it’s a pain in the ass because you need an allen wrench and screwdriver to take the gun apart. It does work well otherwise. I use an accu-wedge in my 3gun AR just to stop the movement/shift which I can’t stand especially when shooting multiple targets at 300yds and beyond.
if the movement is going to bother you buy, the wedge it is the most cost effective solution I’ve seen. Peace of mind is priceless
If it bothers you, put a number 7 O-Ring on the front takedown lug on the upper.
I’m a uniter not a divider.