I shoot lots of lever guns and you do need to crimp for them. The rounds in the tube are under great pressure from the spring being compressed, and when you add in recoil, the bullets can, and will, set back into the case if not crimped. I've seen this happen more times than is necessary. You'll know if this happens, since it usually locks up the gun.
I also shoot two M1A's. I use IMR 4895 powder for all my loads for them. Some swear by Varget, too, but I've found that I can get 1" groups at 100 yards with both my standard M1A and my National Match, using good bullets. I do crimp my loads for the M1A, since the rounds go through a pretty violent transition from the magazine to the chamber.
Hope this helps.
Fred