Loads listed for the standard .45/70 Trapdoor should be able to be used in the .43 Mauser m71 with same weight bullets, due tothe Mauser's greater capacity.

To simiplify and use smokeless powders, I've come to use and like Hodgdon's H4895 Extreme. This powder gives exceptional results in reduced loads, whereas many other smokeless powders do not like to be reduced. H4895 can be reduced to as much as 50% and still give good results.

In the larger .450 Alaskan case, I used 45.0gr. H4895 with a 500gr. cast bullet and Remington 9 1/2 primer. The velocity is 1,530fps, which matches closely with the largest .45 calibre Sharps rounds used in the buffalo rifles. It is a VERY capable load. With a 490gr. lead bullet form a different mould, the same H4895 load produced 1,495fps. Both bullets were cast from WW and were of gas check design, with checks attached. Accuracy was decent (4" @ 100 meters) for the short barrel and iron sights. Did I mention my barrel was like a sewer pipe inside, untill I fired 40, polishing loads through it. It's still quite bad, but shines slightly in places. With either .43 Mauser or my light .450 Alaskan loads, it will do for any moose, elk, boar or bear for that matter.

Other loads I tried, were 35.5gr. IMR3031 with 420gr. RCBS cast GC bullet - 1,526fps and 50.0gr. H4895 with Lee 400gr. plain base for 1,640fps. No pressure signs whatsoever.

The .43 Mauser case is noted to have a 77gr. capacity, some 7 to 10gr. greater than the .45/70 actually has. Thus, with a similar weight bullet, the same load should produce lower pressure than the .45/70 produces, even with the slight size difference. (.010" only)

"Modern Loading" by Richard Lee contains loads for the .43 Spanish, which is quite similar to the .43 Mauser case in design and shape. He reduced .45/70 loads by 10% "for your safety".

These .43 Spanish loads are listed as maximum loads ie: reduced .45/70 data)

AA2495 - 44.9gr. - 378gr. lead - 1,547fps - 13,050CUP
AA4350 - 48.5gr. - 378gr. lead - 1,317fps - 13,860CUP
Re#7 - 31.4gr. - 385gr. lead - 1,334fps - 14,670CUP
AA2495 - 40.4gr. - 475gr. lead - 1,440fps - 14,400CUP

In Acurate Arms testing, even the original-type of Military factory .45/70 load laoding of 405gr. lead bullet over 70gr. of black powder, produced over 22,000PSI using today's GOEX powder. Thus, you can see what low pressures are being generated here, with the above loads, yet the ballistics are similar to original, or better - generally better & could be improved upon with judicious loading, as I did in my even larger case.