Forming 45-70 and 45-90?

[Naphtali]

45-70 and 45-90 brass have extremely slight tapers from head to mouth. "Blowing" them out to accept .476-inch bullets, as 475 Linebaugh and 480 Ruger brass are, in essence, blown-out and shortened 45-70 brass is probably doable. What sort of loss from brass rupturing near case mouth should be expected when using 45-70 and 45-90 brass full length? What I anticipate is a higher failure rate from longer brass because Linebaugh and Ruger brass require less expansion at the mouth. Shorter brass' mouths are closer to .476-inch for mouth inside diameter because less taper has occurred.

What sort of loss percentage should be expected from virgin Starline brass?

[17nut]

I have formed 12,7x44R (Scandinavian 50-70) from 348 WIN for the past 30+ years and have never ever lost a single piece of brass due to expansion near the base.

204535
204534

[Steelshooter]

Starline is excellent brass, they make it in both calipers you listed.

[ARKLITE881South]

Starline is excellent brass, they make it in both calipers you listed.

VERY true, i wouldn't even mess with making it myself, Starline is the way to go.

[reed1911]

If I understand you correctly, you are thinking of a full length .475 caliber from straight .45-70 and/or .45-90.
Provided you anneal the mouth area, I would expect 0% case loss from blowing them straight.

[Naphtali]

If I understand you correctly, you are thinking of a full length .475 caliber from straight .45-70 and/or .45-90.
Provided you anneal the mouth area, I would expect 0% case loss from blowing them straight. You are encouraging.

[reed1911]

Lifetime of forming cases for unique cases. I have to say a .45-70 or .45-90 set to .475 will be a humdinger of power, assuming you are going to load to current pressure (56K-60K).

Quick calc on the volume would be 72.7 based on the 45-70 and 84.0 based on the 45-90.