Took the stock back off and am going to do more work, I'm convinced there must be some stress in the mating of the receiver someplace. Yesterday I tried 180 vld's driven by RL22 and the numbers were quite impressive (the winds had backed off just enough that I didn't worry about the labradar blowing over). I also put a hellfire brake on to tamp down the muzzle left somewhat and that definitely helped--but talk about LOUD report, it's up there with the biggest cartridges I fire. Groupings are still mediocre unfortunately.
