I was loading to 50k in the .45-70 with no problem. The lever tweaked above 60k and yes it was wildly stupid. But my face was not behind the bolt because I do know that the locking block and lever are the most likely points of failure on Marlins.
A benefit of the longer COL of the .45-90 is that I can now dial the pressures back and still get better performance. It'll achieve well over 4000 ft-lbs at the .450 marlin MAP of 43.5k psi.
