Personally I wouldn't use a fat rat and fireform cases to gain that little amount of velocity.
Agreed, that was my main reason for going with the 243 LBC instead (BHW's version of the 6mm AR). Forming brass from 6.5 Grendel is no different than just resizing fired brass for this one, it's just a straight neck-down with no shoulder or body changes. My accuracy load does 2920 fps with the 95gr Berger VLD (24" barrel, rifle gas), although others like Smack on this board have reported 3000+ fps with the same bullet.
