im getting a No.4 converted into 45-70, makes no economic sense but I wanted a 45-70 bolt gun and I like the no.4 peep sight.
You can also do conversions to 40-60 Maynard, .405 Winchester, 40-70 Sharps, etc. The advantage is that no conversion is necessary other than a new barrel - rim, head, and body dimensions are almost identical. So magazines and bolt heads work just fine as is. And... there's lots of cheap .41 caliber bulk cast/swaged handgun bullets of just the right size to play with, aside from the serious rifle rhino roller loads. The Maynard would probably be the best choice because it has regained some of its' popularity with the black powder crowd. Most of the old .40 caliber cartridges when chambered these days are actually done with a .41 caliber reamer.
You could stick with the original .40 caliber bullet sizes; no problem when you're sticking with cast bullets and handgun bullets, but tough to find .40 jacketed rifle bullets these days. There are numerous jacketed rifle bullets available for the .41 calibers, however, such as the 405 Winchester.
I don't think a 415 grain cast bullet with a big flat meplat at 1750 fps or a 300 grain Barnes X at 2300 fps is anything to sneeze at... That's about what you'll get using the .303 British case converted to a straight walled case and of a length that will fit in a LE receiver, within the working pressure of the #4 action. Just take the neck and shoulder out of .303 brass, and you're ready to go.
Makes for some interesting bush guns for nothing more than having a new barrel chambered and fitted. And reloading dies, of course. I had a bubba'd LE once that was then morphed into 40-60 Maynard, but in a temporary moment of insanity, it became one of the few rifles I have ever sold after acquiring them. Got to get a new one built one day.
Your project is only worth what you want to throw at it. If you are happy and they shoot good who cares.
