just picked up a custom build on a siamese mauser action.
factory 300gr jhp stuff seems very mild.
can i take this up to .458 levels or is the brass too weak?
thanks.
lee

The 45-70 loaded to 50,000 CUP for the Siamese Mauser will only push a 300 grain bullet 2530 fps in a 24" barrel. The 458 Win Mag loaded to 50,700 CUP for a bolt action rifle will push a 300 grain bullet 2780 fps in a 24" barrel. That's a difference of 250 fps. So no, the 45-70 cannot be loaded to 458 Win Mag levels. Not even close.

It is a NO to answer your question. However, you could load the 45-70 up to the "modern" ballistics. Hodgdon has some data for this but I am not sure if your "odd ball" rifle will be able to handle a hotter load. I would leave it alone if it is not certain that the rifle is strong enough or not. Good luck.

I had one in a few years ago to correct feeding problems and something else, don't remember. Worked up loads for 350 and 500 grain bullets. If it's light enough, it will feel like a 458.

What's wrong with the Siamese mauser, Mingo?

In my Pedersoli Sharps I use Vithavouri 133 powder for hunting. In Sweden we can�t hunt with BP because it�s forbidden by law. If we want to hunt we must use Pyrodex or modern powder.

The Vithavouri 133 gives the lowest pressure and the highest velocity. I modern bullets, but know I shall start to use bullets of lead too.

Remington 300gr hollowpoint, 55 grains V 133, velocity 2073, pressure 20,000 CUP

Hornady 300 gr hollowpoint, 55 grains V 133, Velocity 2116

Hornady 350 gr, 52 grains V 133, velocity 1984

Speer 400 gr, 49 grains V 133, velocity 1870, pressure 21,000 CUP