I have a bunch of commercial ammo to test out, including Prvi 139 grain FMJ's (I've had great success with Prvi, though Hitzy has me worried) and some higher end Norma Vulcan 156 grain and Norma Nosler Partition 140 grain. I will eventually get set-up to reload for 6.5x55.
I didn't shoot those, but the PRVI 139sp. I do load their 120bthp and they are very good. Those FMJ might be better....
This 117 year old sporter shoots them like this...my S&L M52 and M69's did not, neither did a CG63 sporter barrel '96, or my Howa or HVA....I initially bought 140 rounds of it, and I still have 80 left. Good brass at least!
