Re: Rem. R1 Enhanced slide not locking after last round
I'm relatively sure it's something amis with the grip change. Possible the new grips exposed the fact that the slide stop is poorly fitted/contoured. I doubt seriously it has anything to do with the recoil spring or MSH.
If you haven't been, pop over to 1911forum.com and introduce yourself. There is a gunsmith section there and there are some real knowlegable folks there when it come to the 1911 and things related.
MSgt USAF (RET)