My current goal is to get rid of the slop between my upper and lower receiver.

Seems there are a couple options that are popular ranked from what I perceive as best solutions to worst.

1. Aero precision AR15 Stripped Lower Receiver, Gen 2 - Anodized Black (has a screw in the grip to tighten down the upper to the lower.)
2. National match shim / accushim (which apparently pushes the upper and lower together instead of apart like the accuwedge)
3. JP MicroFit™ Front and rear Takedown Pin Sizes .247, .248, .249, .250 (there are also a type of “tensioning pins” that i can no longer find available new generally)
4. AccuWedge (which i dont like because it forces the upper and lower farther apart to remove slop)
5. Takedown pin shims
6. #21 O-Ring. 5/8 x 15/32 x 3/64. for a kitchen/bathroom faucet. Ace Hardware.(others have used tiny rubber bands for hair, soft metal wire, etc. )

A combo of #2 and #3 would cost somewhere around 40$ vs #1 @ around 100$ curious if anyone has any experience with them here since they seem to be the best two solutions for a common problem.

Power Custom Upper Lower Receiver Shim Kit AR-15 Pack of 10

A pain to get in, but they work great. Should only take one in the front.

I use aluminum tape on the underside of the upper where it is widest to eliminate vertical looseness. Attached is a quick shot showing location.

IMG_0441.jpg

The tape stays stuck, never comes loose or shifts. Generally takes two layers to snug things up. I generally lay down a wider than needed strip and use a razor blade to ride the sides (outer and inner) of the upper for a clean trim. Aluminum Black applied to the edges blends out the white edge.

No idea whether it helps accuracy, that's not why I do it. I just don't like the feel of the loose upper and lower.

Why? There will be movement simply due to the nature of the design. This movement will not affect accuracy. The ammo you choose will have more affect on accuracy than any of these shims to eliminate play between the upper and lower.

Not knowing whether upper or lower has the tolerance issue, what makes you think a new lower is going to solve the problem? Unless you walk in with your upper and a set of pins and keep trying lowers until you solve your "problem" or quit. The JP micro pin set seems the best place to start if it bothers you that much.

Legitimately, there is an armorers gauge for the ears for the front pivot pin on the lower to make sure it hasn't worn oversize. I doubt this is your problem. t's a parallel block 2 in x 0.750 in x 0.750 in. An end is machined 0.750 long and 0.515 in wide (+ zero/-0.002 in.) and shouldn't freely drop until the end of the gauge is level with the bottom of the ears.

Cyphertext has a point also, the sights are attached to the upper, so the bullet is going where the sights are. Will the wobble affect match grade accuracy? Probably, but then you didn't buy a Sport II to shoot itty-bitty, teeny-weeny groups.

Thanks Tiribulus, I've read that they do a decent job and are hard to get in. Some people who it did the job for wish there were more thicknesses available so they could use 2, one on each side so that it was more centered as opposed to having one larger side pushing it off center. what do you think about this?

I agree, don't like how it feels either, and I think everyone can agree it will make a difference in accuracy to one degree or another, how much everyone can discuss. I had hoped to stay away from stuff that might melt or become sticky, that said aluminum tape sounds like a good budget option if you don't care about that factor.

1. Aero precision AR15 Stripped Lower Receiver, Gen 2 - Anodized Black (has a screw in the grip to tighten down the upper to the lower.)

Uh, no it doesn't. It puts upward pressure on the tang of the upper that the rear pin goes into. While it may reduce movement, it doesn't "tighten anything down". And that still doesn't answer the question as to exactly why you have what you consider excessive slop between upper & lower. A different upper might get you the same result.

How does slack between the upper and the lower cause a reduction in accuracy?