Simple, 450 Marlin...
Phil
I have to agree. The 45/70 brass is very light duty, it deforms easily. The Marlin's are quite clunky and rough and I did not feel confident with full power loads( by the book) The .450 Marlin is heavier walled and webbed and I no longer worry about these things.
Selling the GBL and acquiring a BLR was a good move for me.
Try Starline and that issue will disappear. I've run velocity up to where I didn't want to take anymore recoil and pressure was about 35.5 Kpsi.
450 Marlin brass has less capacity, so pressure is higher at a given velocity, assuming all else is equal. The .450 Marlin is a modern, high-pressure version of the .45-70, and lends itself well to a bolt-action conversion in any Short-mag rifle. That's where I like it, run it up to 50 Kpsi and you have a duplicate of the .458 American.
But not all .45-70 brass is as easy to bend as two types I've used, one is WW, the other was Remington .45-70 redrawn to .45-90. The re-drawn Remington brass was so flimsy I could bend it by chamfering/deburring. I got 300 rounds of that stuff dirt cheap and after I started loading it, I saw why..
The Starline had to be annealed to get it to seal at 21 Kpsi, or the whole case would soot up.
My Guide gun's action is not at all rough, actually quite smooth.
