Thursday, October 18, 2007

RCBS Lube-a-matic Fun with .45-75 Bullets & More

Well, today I cast some bullets for the .45-75 using the Lee 458-325 mold (another story) and went to lube and size those that were suitable. Well, well. First I can't get lube pressure. Next I find that the O-rings, both of them, are blown. Then I find that I've lost my manual. Fortunately RCBS has one on-line. Now I want to order the O-rings and RCBS's on-line ordering system is down tomorrow and Friday which evidently includes today on their calendar (of course...). So, I got a few bullets done. Wish I could have done more.

Then John Kort posted the following at the forum:
For reference purposes from Winchester's 1895 Catalog:

.45-70-350 Winchester - 1,307 f.p.s.
.45-75 Winchester(350)- 1,343 f.p.s.

The .45-75 was never factory loaded with smokeless powder, probably due to the short life of the 1876 Winchester.

The early smokeless powders used in the .45-70 were DuPont No.1 Bulk Smokeless (1895-1905 approx.) then Sharpshooter (1905,approx) thru 1950's).

DuPont No.1 Bulk Smokeless had a burning rate similar to 4198 but it was loaded to fill the case like b.p. Sharpshooter was similar in burning rate to 2400 BUT it was a disc powder with a hole in the center for more even burning with the airspace in the case.

Both powders were also used in cartridges as large as the .50-110 Winchester.

Based on the early factory development of smokeless cartridge options for low pressure b.p. cartridges, smokeless powders between those burning rates would be ideal. In the middle, is XMP5744, a modern day propellant especially designed for b.p. cartridges. 4759 would be another good one.

Here’s some relatively current data for the .45-70 with 340-350 gr. lead bullets with both XMP5744 and H4198, which I prefer over IMR since Hodgdon ‘s version features a smaller grain for easier metering. Perhaps now, though, since Hodgdon distributes both, they may be the same(?) like they did with H4227 and IMR4227.

340 gr. lead (Accurate Arms Data)
XMP 5744 / 27.0 / 1,314 f.p.s.
XMP 5744 / 30.0 / 1,494 f.p.s. / 14,600 p.s.i.

350 gr. lead (Hodgdon Data – Manual No. 26)
H4198 / 28.0 / 1,159 f.p.s.
H4198 / 32.0 / 1,387 f.p.s.

Since the .45-75 case holds a bit more powder than the .45-70, use of the above data should result in slightly reduced ballistics...maybe 50 – 100 f.p.s at the most.

Time will tell………

I've now gotten most of the old lube out of the tube (boy that stuff is stubborn!) and am about ready for some SPG. Going to order some this morning.

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