One of the things about driving all day, every day...
It gives you lots of time to think (sometimes even in depth, seemingly intelligent stuff...key word there is seemingly)
Today while cruising in the snow I was trying to reason out why dies are made to size the mouth at .450" (ID) and deciding if I knew how to make my own dies. RD got me on the right train of thought, neck tension and seating depth.
When looking at cartridge drawings (
http://www.leverguns.com/dimensions/images/4570.jpg ) and reading, its always suggested that the 45-70 case tapers from .500 or so (some drawings vary a tad here) down to .480" (OD) at the mouth...but I "THINK" the drawings left out a measurement.
They don't show the measurement across the brass at the base of the seated bullet...the brass is supposed to taper to .480" (OD) at the base of the bullet and then its straight from the base of the bullet up to the mouth...its not supposed to taper all the way up (the fact that I have been overlooking)
Any die made to size the brass this way would be bullet specific (as far as seating depth goes)...At first thought it would seem you could engineer the die around the bullet that seats the deepest (the RD 425 in my case, YMMV) and make it so the ID of the mouth is .455", but if you did that then seated the RD 350, you'd still have a slight bulge at the base of the shorter bullet...
At least now I understand why we have the bulge...can I make a die (or dies) that will eliminate it? I think...but I'm holding off judgement on that for now .
Now I'm wondering about Marlins chamber specs...and if that will cause any problems.
This all boils down to seating depth though....back in the day, most of the bullet was outside the brass, not in it.
And after today...the 450 Marlin makes a lot more sense to me than it used to, it serves a greater purpose than just keeping hot loads out of old guns...it solved other issues too...but I still don't want one
You guys probably think I'm nuts for pondering on this like I have...but thats just the way my mind works. I have to "understand" why...somebody (RCBS, Lee, Lyman, and Redding for example) telling me "because thats the way we make them" just doesn't do it for me.