I'm building a .505 Gibbs bolt gun for use as an Alaskan brown bear back-up gun and I want it to be handy in the brush. Anybody have any experience or recommendations on minimum practical barrel lengths? I know it's overkill for Brownies, but I like the nostalgia of this grand old cartridge, and since it is overkill, I'm not worried about maximum velocity, just trying to avoid excessive muzzle blast.