I use Cast Performance 405 gr WLNGC over 48 grains of H4198 with a Federal 210 primer for 1920 fps in my Marlin 1895 Guide Gun. Those bullets are gas checked. I’ve never slugged my bore.
These loads are pretty darn accurate for a short handy lever action. I put a 4 power scope on it just for accuracy testing and got 1.25” 100 yard groups. I pulled the scope and hunt with an XS sight systems ghost ring. It’s a handy and powerful thick woods carbine.
I’ve killed a large cow elk by putting one shot in the “boiler room”, massive blood loss. Also a one shot kill on a decent sized mule deer buck in the same manner as the elk with the same results. I loaned the rifle to a friend who took a Kodiak bear with one shot. I believe he was using 430 gr hard cast loads and the bullet broke the shoulder, traveled through the body and broke the opposite hip.
On family hikes and camping trips it’s what I carried when we lived in AK.
What 45-70 do you have? Keep in mind these are Marlin only loads. If you do not have a very strong action, do not load this hot.