Interesting that playing with the pressure before bullet release effects accuracy.  I noticed my Krags seem to group better with loads using faster powders that give less pressure at bullet exit.  I have no idea about this thing I put on the end of my Garand, haven't shot it yet.  It grouped good with the repro pronged flash hider, but I never got down to comparing it vs shooting with the stock muzzle other than to say I thought it shot better.  I like having something out there, when I get tired in prone I can rest the barrel on the ground without damaging the crown or getting dirt in the barrel!  The way the butt comes up with the weight of the scope and mount out there, it just might bounce off the ground a few times!  Scope and mount total 1lb 7oz, without rings. 10.7oz of that the mount.  The laminated handguard 1.75oz.