You need a firm crimp on 45-70, or ANY round chambered in a tubular magazine. Recoil separates and slams the shells back together in the magazine, which will push the bullet back in the case if not crimped (also the reason of using flat point or round nose bullets, and not pointed bullets in a tubular magazine).
There are three kinds of men:
1) The ones that learn by reading.
2) The few who learn by observation.
3) The rest of them have to pee on the electric fence and find out for themselves..........