A friend a few states away from me is having trouble with building her lower.  By all pics the bolt catch looks like it is too wide and not centered to contact the follower.

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I think she might have gotten an AR-10 based .308 LPK by mistake. The bolt catch, for one, is beefier and wider to fit centered in the larger platform's magwell. About 90% of the AR-15 and AR-10 LPK parts will interchange, but not all of them - at least not without modifications.

Thats what it looks like.   What a pain in the ass.   I'm helping a first time builder in Florida while I'm in VA, thinking she has done something crazy and troubleshooting and pics and videos and many many questions and finally figuring out its a wrong part.

Finally figured it out when I told her to slap a mag in there and it showed how out of alignment things were.

Still thought I was crazy and came here to confirm sizes of the catch.

A basic one in one of mine looks to be 1 inch, +1/16 maybe.

That's not an AR-15/M16 bolt stop.

@CousinIT50 ^^

And I'll be a standby JIC. I'm going to be taking off my POF bolt catch and replacing it with an FCD ABC, plus I am awaiting a box of gifted take offs, and there's a Colt (Schmid maybe) OEM catch in there as well.

Hmmm, it looks like a 10B catch cut with a 10A angle on the thumb side. Odd.

https://762ar.com/technical-information/visual-differences-m15-ar-10b-and-ar-10a-components-ar-10a-versus-the-ar-10b/