45-70 sizing??

[hiram]

The throat on my 45-70 rolling block is .050" long and .4595" in diameter.

The bore is .457-.4575".

I can take an unsized cast bullet (.464-.463), seat it in a case so as to be short of the throat, and the cartridge chambers with no forcing.

What do I do? Size the whole bullet to .4595" (throat size) or just size the front band and leave the rest of the bullet oversize?

[leftiye]

Either way would be about equal. Filling the freebore is first in importance. A question to consider is what kind of shoulder there is at the end of the chamber neck. If it is sharp, it will probly shave lead. Unless it is smooth and/or rounded it will not make a very good sizing die. This needs to be balanced against the idea that sizing before firing, then bumpimg up under impact and then sizing down again while entering the freebore cain't be good for the final shape of the boolit (if you pre size).

[JRW]

The latest issue of BPC news has an article regarding the compression of black powder with 5 different powders. the results are interesting because some of the smallest groups were shot with up to .250" jump into the lands. If you are shooting the holy black, probably won't have to size at all, but try both to see what works for your rifle. You may be able to pull the article up on the net, or write or call them for a comp copy, Great Mag for the BP shooters. Jim

[montana_charlie]

What do I do? Size the whole bullet to .4595" (throat size) or just size the front band and leave the rest of the bullet oversize?
Size the front band (if you have to) and leave the rest as cast. You shoot soft alloy over Black, so the bullet will get that fat anyway...as soon as the light comes on...before it starts to move out of the case.
Doesn't make much sense to size it down, then bump it back up.

It would seem your chamber is a bit generous (in the neck area) to accept a bullet that fat...unless you have some unusually thin brass.

I was looking at your chamber cast picture.
I used the picture to take some crude measurements with a dial caliper. It seems to indicate the chamber step is 10 thousandths high...which is about normal for most 45/70 chambers.
That makes me wonder (again) about the thickness of your case mouth wall.

CM