I figure velocity with the 230 grainers is probably right on the ragged edge between stable and not. I'll get 1 to 2 keyholes a cylinder (without any particular pattern as to which chambers). I don't handhold, and don't know if this helps, but Wilson made hollow base 230 grain ball cartridges at one point. That particular load did not key hole. I'm thinking the hollow base allowed the bullets to bump up enough in the chambers and engage the shallow groove rifling just a hair better to keep it above the threshold for stability.