I have both a 450BM and a 450BM-C (Corvette). I have three .450BM bolts, one from the factory and 2 made from .223 bolts with 7.62 extractors. They have been fine (but I have a spare) and I have not heard of anyone breaking one. The stresses are not in the right direction to cause any problems with the thinner skirt of the bolts modified for the .450BM.

Good choice BTW. Same reasons I went with the .450BM over the .458SOCOM.