For years, the lack of 308 AR standards has been a source of nonstop headaches for manufacturers, for there isn't a TDP for 308 ARs that defines acceptable dimensions and tolerances.
We'll limit the topic to bolt catches in this article, as it is a frequently asked question.
LR308 used to be shipped with 223 spec bolt catches. CMMG has a version with reinforced area on the mag follower trip, the area behind the lower paddle is also changed, see illustrations below.
The radius behind the CMMG designed (on which 308 ABC/R v2 and v3 are based) makes it incompatible with 223 lower receivers. However, a 223 spec bolt catch almost always works on LR308 pattern lowers.
Note that 223 TDP spec, and CMMG designed 308 bolt catches are incompatible with KAC SR25 and LMT MARS, but it is compatible with LaRue 308 ARs which look to be SR25 pattern. If this isn't enough to drive one mad, remember this is but one single component. Take down and pivot pins are also different, among a host of other components.
The aforementioned lack of standards for the 308 AR means everything
made for the 308 AR needs to be followed by a caveat when it comes to
compatibility.