OK, I tried some Oregon Trail bullets today (because I had some), and got what I expected...bad leading in every load but one.
The pics show the severity after only 6 rounds of 11.5gr 2400 under a 158gr SWC from Oregon Trail, but I got similar results with all the following (all in Starline Brass with std primers):
11.5gr 2400, 158gr SWC -Oregon Trail
11.5gr 2400, 158gr SWC - MBC
8gr Power Pistol, 158gr SWC - MBC
6gr Green Dot, 158gr SWC - Oregon Trail
6gr Green Dot, 158gr SWC - MBC
However, I got no leading (or very little) from 17.3gr 300-MP using the Oregon Trail bullet (but I do with the MBC bullet in the same load
). The 17.3gr load is hot, so I am assuming that my other loads did not provide enough pressure to prevent gas blowby.
Interestingly, the "book values" for pressure on the above-listed loads are approximately:
2400 --> 25,000 CUP
Green Dot --> 34,000 CUP
Power Pistol --> 33,000 CUP (estimated from a JSP load)
300-MP --> unknown (of course :banghead
According to MBC, that 25k CUP load with Alliant 2400 should be close to optimum for their 18 BHN bullet. I have found no load, hot or mild, that works with their 18 BHN bullet, but have used their softer ones with success (primarily in 45 Colt).
I guess my experiment is over. I'm going back to softer lead when these are gone. I suppose I can use the Oregon trail bullets for VERY hot loads w/out leading.