Herman,

I think the issue with your .50 can be summed up in 1 word.............." Length" .
Fast twist barrels need long bullets to stabilize well - and since copper is lighter than lead, copper bullets like the Barnes or copper-jacketed bullets like the SSTs are longer than the pure lead DCs for any given length.

To be honest - this is probably the same problem with your .45 too. IMHO, just about ALL of the bullet offerings for the .45s are just too darn short (light) to work well, ESPECIALLY if you have a 1:28" twist in your .45.