I installed my RRA LPK into my RRA stripped lower.

It went off without a hitch other than my vise grip pliers slipped and chipped the anodizing a bit around the bolt catch. A little sharpie and it's hardly noticeable and at any rate it's one of many more marks to come if M16s that I've used are any indication.

One thing I've noticed though is that the hammer pin seems to rotate with the hammer, is this abnormal? Is there a specific direction that the pins should be installed? Function check is perfect. As long as the pin isn't going to walk out due to being installed incorrectly, I honestly couldn't care.

The only other issue is the end plate on the stock. The little nub that goes into the lower receiver to keep the plate  from rotating is bigger than the indent in the receiver so there is a gap. The stock is secure and isn't going anywhere so it's only a cosmetic issue. Would an RRA plate work on my military sized LMT buffer tube? I'm guessing there wouldn't be any problem with fit if it were an RRA part.

Pins will rotate.

The end plate isn't so tight in ID that it would bind on anything

Though even if it were made tight the LMT tube is mil spec and thus small in OD than the RRA tube.  Should be fine

Never heard of an end plate not fitting as you described...Odd.

Interesting. Perhaps I'll try and take a picture of the end plate.

are you sure that you didn't catch a piece of the spring (for the take down pin) in between the end plate and receiver when you were tightening it?  That's the only thing I can think of that would cause it not to be a tight fit.

Nope, this is an issue I saw before assembly. The receiver is obviously smaller in that notch than the endplate. I see other ARs in picture threads like this and like I said, it still somewhat locks into the hole and with the tension I have on the castle nut + blue loctite, it isn't going anywhere without me removing it. I'm just assuming RRA has a different tolerance for the part than LMT.

Buy another plate, if the plate is out of spec.   Get one of those ambi type plates that have other options for sling attachments.

I ended up giving the plate a few wacks/taps with a hammer and it snapped into place. It must not have been that out of spec or it was just binding up for whatever reason.