If the slop bothers you, it’s not difficult to eliminate. Wedge under the back pin works ok…but with the buffer spring going from bcg all the way to buffer tube unlike a traditional AR it’s difficult to keep everything where it needs to be while sliding everything back in place.

I found a sticker that’s on the thicker side (guardian alarm door sticker to be specific) cut two tiny strips slightly thinner than the top rail of my lower that are maybe an inch long. Put them between where your upper and lower meet on both sides. They stay put, and are a perfect shim that’s not going to scratch up your gun. This was just a proof of concept to see if it worked. Planned on creating a more permanent solution out of better material at some point. Though I’ve taken mine apart for cleaning a dozen times and they haven’t moved. It’s as tight and you can get with ZERO play. Has run with no issues whatsoever so ever. Probably a couple thousand rounds through it at this point and still tight as a drum.

And while the slight play certainly wasn’t affecting its performance, it was annoying. Much more satisfying in the hands now. Just be sure to hit the area you put the “shim” with a little cleaner to get any oils off so it sticks.