09-03-2018, 07:35 PM
(This post was last modified: 09-03-2018, 07:39 PM by centerfire.)
Klem nailed it first try. Ejector swipes ever fourth or fifth round plainly means you have excessive pressure. You don't have a fast barrel, you have a set up that conservatively shows pressure signs. You're getting the velocity of a 20" barrel because you are probably loaded around 60k psi. CL is a great tool for estimation but should only be used to start a load, not predict absolute pressure. Your broken bolts have clearly told what is going on, you've just ignored the actual problem. You're handloading a cartridge that does not tolerate excessive pressure, prolonged pressure signs will (have) yield catastrophic failures. Grendel should be worked up to the correct velocity, not pressure like most other cartridges. If you want to push the cartridge you need a stronger platform such as a bolt action.