The rim size between the two is slightly different. If using American 6.5x55 brass (same rim as 30-06 family) they will most likely have the same rim size, but as I discovered in my Barrett Fieldcraft the Lapua brass has the original European (larger) rim and will not fit the Barrett. I had no trouble with the Hornady, Federal and Nosler brass. My wife's Ruger MKII 6.5x55 will feed anything
