Originally Posted by
Bigslug
All of these questions are worth looking into.
I doubt very much that the MKI .38 would do anything more than punch a straight hole. At 600~ fps, I think even asking for significant deformation is a bit much. The 358430 I Jell-O tested years ago was HARD, but as it is basically a blunted cylinder, it showed ZERO sign of trying to deviate off course. The MKI is basically the same bullet up-sized for a .360 bore with a different groove configuration, so I wouldn't expect much difference in behavior.
The .455 MKI and MKII conicals MIGHT be tumblers, but then again, because of the hollow base, they may actually be pretty well balanced to keep moving through tissue point-first. That's one I'm in a position to test the authenticity of. I have a veritable army of well-disciplined milk jugs willing to make the supreme sacrifice. I'll get back to y'all on that. One thing I have noted in my execution of the dreaded dog food cans is that the nose profile tends to cause it to skip. I set the cans up some yards in front of the berm, and have found a large percent of my .455 slugs laying on the berm with skid marks from where they passed the can and bounced. I'm probably running a little harder than Queen Victoria's original spec, but at 700-ish FPS, I doubt it would pancake much unless you cast it from marshmallow cream.
As to my NOE 200 grain RN, it might be a tumbler with its longer nose, but as it technically isn't an authentic bullet, we'll only gain insight into what might help us today, not what the Brits had in mind 80 years ago. I suppose the truth is in the milk bottles. . .