14 January 2022
Wolfe's book on reloading the .45-70 for Trapdoors in writing the book measured several bores which were .460+. The shooters at Windhill also measured Trapdoor bores again with bores running up to .463. Wolfe thought these were deliberately oversize to lessen the effect of powder fouling.
My present Trapdoor has a bore running .460 with a smooth bore. I load a soft bullet of 30:1 Pb/Sn alloy, very soft. The bullet is the SAECO 1881 500 grain round-nose dropping from the mold at .459 from two two-cavity molds. Powder charge is 68.5 grains Swiss 1 1/2 compressed with two wads, .030 and .060.
According to Wolfe, the soft bullet will swell up to fit the bore upon the ignition of powder. I've not measured bullets after firing, but have dug them up and see the marks of the lands fully engraved on the bullets.
This load is also what I shoot in my Sharps. The Sharps has a .458 bore. It does not have the flatter trajectory of the SAECO 540 grain semi-pointed bullet, but I score better at 600 yards with this load.
The 540 grain semi-pointed shoots as well on paper at 100 yards. I sometimes think I know more then I understand about the black powder loading for the .45-70.
Four decades ago, I was given several .45-70 405 and 500 grain Lyman molds that came in gray boxes. These were measuring the bullets fresh out of the molds, they were .462 and 463. These did not shoot at all in my Marlin 1895 .45-70. When I complained, one Windhill shooter offered to buy these molds to be able to shoot smokeless in his Trapdoors, he got a good deal.
This decades ago era of grey box Lyman molds were known for oversized bodies and undersized noses. In contrast, the RCBS molds 45-405-FN and 45-500-FN dropped at .459 and shot well with Reloder #7. I cast and shot the RCBS bullets. They were sized in .459 die to only add lube. This alloy was 94/4/2 Pb/Sb/Sn.
Perhaps you can find one of this earlier era gray box Lyman molds.
Farm boy from Illinois, living in the magical Pacific Northwest