Problems . Bought a Mk V accumark used under 50 rounds thru it( Came with new and once fired brass,Dies and 2lbs of Retumbo and Leupold scope I've since sold,deal of a life time,couldn't pass it up). Previous owner used Leupold Standard rings ,after 40 rounds recoil destroyed those rings. Installed a Ken Farrell industries rail on it designed for WBY Mag.But rifle shot hard right,so I installed Burris signature rings with off set shims.I was then able to zero rifle. The directions with Farrell rail said recheck screws and recoil lug screw after first few shooting sessions. I noticed a few shots would be on the money and then next group was way high and to the right !!! So I re-checked screws and they were a little lose. Directions said the rail is settling in. So back to the range tomorrow,the factory brake is fine for shooting standing up,but not off a bench . I bought a Terminator 5 port T4 and it was unbelievable the recoil reduction,but oh the muzzle blast was huge. Anyhow any one have experience with these big boomers,any suggestions ? Looking back I wish I save my cash and bought a 6.5 PRC ,but I love guns like us all.