I know there is no guarantee that another brand upper will fit the M&P since there is no Milspec to follow. I would like a .260 Rem upper and still keep my 7.62 upper.

I know there are two manufactures loading the 6.5 Creedmore vs 1 for the .260 but I'm more worried about long-term brass availability and there will always be .243 brass to neck up or .308 brass to neck down. I think absolutely identical magazine feeding is an advantage of the .260 over the 6.5.

Mike