The damn stickies! I read through them a few years ago but had forgotten all about them. Thanks for the reminder...very helpful.
According to the sticky, the other two buffers don't have the groove cut near the threads like the German buffer one I posted above does. The German one also has a bit larger diameter nose cap at 0.902", the other two assumed Yugo buffers are at 0.883". I was able to fit one of the two Yugos into the receiver and there was absolutely no bind on the bolt extension.
Tapering the nose cap would definitely rid of the bind. As would a buffer with a smaller nose cap.