I have shot alot of 45-70. I have shot hot loads, light loads, heavy bullets, and light bullets. The 405 grain bullet at 1600fps is probably optimum. Alot of peopleshoot the 300 grain at 2200fps to flatten their trajectory. I do not believe it flattens the trajectry very much-some yes, but not very much. As far as performance on game-a 405 at 1600 fps will take anything you want to shoot, without the recoil punishment. You can push them faster, but their truly is no gain in "Killing Ability".
Thekey to the 45-70 is practice. The beauty of the 45-70 is how cheap it is too shoot.How well it shoots. And how easy it is to reload. Go out and buy1000 lead bullets, or better yet a pot,mold, and some lead. Then cast away. It is actually very easy. Then shoot, shoot, shoot.
I have seen alot ofshooter's wholike the Barnes 300 grain bullet. Ihave not shot this bullet. I have looked at it with interest, but when it cameright down to it, I could not justify buying them. Yes, it is ballistically better than my cast 405's. I just can not understand what it is made of that makes them so expensive(solid gold).
I shoot the 45-70 for nostalgic reasons. I like the lever's and the single shots. To me modern bullets just do not seem to fit in the 45-70.
As far as the load to use, well that is easy. Fill the case up with 3F Blackpowder, lop off the excess with a butter knife, and seat the bullet. A little crimp is alright if you shoot a lever, but not necessary in a single shot. You will not believe how many loadings you can get out of a case with a single shot, and no crimp. Especially if you have a tight chamber cut.
I like the guide gun. Is yours ported? That short. ported barrel model in SS would be a great rifle. I just might have to get one(it just seems too modern). For now I shoot my 1886's, and my 1885. I have read on the levergun site that they recommend a heavy crimp for theGuide Gun. Whenever I heavy crimp, I use a taper crimp instead of a roll crimp. I use the Redding taper crimp die, it works very well. I crimp in a separate step, I never crimp in the seating process. I believe I get a better "feel" if I use a separate step. And it allows for slight casing discrepancies(?). If you want that heavy load go with RL 7. I have also had great success with 2400. Tom.