Bugger:
The bolt 45/70 Siamese conversion is an entirely different beast. I have 3 - one for me, one for my wife and one spare. Also, have a Win 70 converted to 450 Marlin and a Ruger M77 tang safety in 450 Marlin. The first two have been to to Africa on PG and my wife's goes every and so does my Win 70. Loads are listed for the Ruger #1's - 350 TSX at 2400. We also take CEB 325gr solids at the same velocity in case of pachyderm encounters. Recover very, very few TSX's and I've tested the CEB's and have never recovered a single one - even end to end though a mountain zebra.
Honestly, IF I was going to do a conversion it would be the same S/M but in 450 Marlin instead. Primary reason is you wouldn't have to open the bolt face making the rim stronger and less feeding trouble/work. My "spare" has a section of the bold face rim broken out and therefore won't eject properly. I've just recently found a micro welding shop and plan on getting the rim rebuilt.
Bugger, PM me your email address if you might be interested in it. I'll send you photos and if interested I'll get it fixed and make sure it properly ejects. Already converted it to the Win style 2-position safety and I think a Timney trigger, Leopold bases and rings.
