On the left is a .45-70 with a 405-grain bullet. On the right is a .40-65 with a 400-grain.
I won't go through the 'how I got started with this' story, suffice it to say it's been frustrating at times. Basic of loading this thing:
You can get cases from Starline, or you can form them from .45-70 brass: anneal, then use a .40-65 full-length sizing die to reform them(this is a 'take your time, a small bit at a time' process). Starline cases are fine quality, but tend to wind up a bit on the short side after fireforming.*
So you decide to use .45-70 cases. Start by annealing the front third of the case. Then, with the .40-65 sizing die and plenty of suitable lube, you resize/reform it a bit at a time: push it in max of 1/2", back out, redistribute lube, do it again, until you've done it all the way down.
Which means your case is longer than it was, in this case a lot longer. So you have to trim it a bit before it'll fully chamber, which you check in the rifle you'll be using it in. Which is where this can get less than fun. Because reports are that some dies won't reduce the diameter all the way down to just above the rim sufficiently. That means you either get another set of dies(expensive), or- if all else is good- you do a little careful grinding on the bottom of the die to shorten it(no, that's not my idea; I read about it in several posts on the subject), which means grind a small bit, deburr and clean up, then use it to resize one of the cases and try it in the chamber until it's a proper fit. Complicate this by Shiloh apparently making these with a tight chamber, and one company makes a die set specifically for them. The good thing being that once you have cases that chamber properly, you should only need to, at most, neck-size them after that.**
All that's because the original cartridge used about a 250- to 300-grain bullet in Winchester lever rifles, and it's now mostly used in single-shots like Sharps and High Walls for long-distance shooting. So the chambers wind up being a touch different, which has caused people to get creative in fixing the problems. Etc.
Why the long bullet in single-shots? Seems the dimensions make it pretty ballistically efficient, more so than most .45-70 bullets, and it does it with a fair bit less recoil, reaching out to some impressive distances according to what I've read.
Yes, I've fired these, with both smokeless and black powder. There really was less recoil than my .45-70 with its long-range bullets. Accuracy seemed good, though real work on that will be after I've got more fireformed brass.
So that's what I've been doing in part of my 'keep from going nuts because most places are closed' time. We'll see how this goes.
*If you've not done this kind of thing, the first time you fire a cartridge case in a particular rifle the heat and pressure forms it to fit the chamber. This often causes the length of the case to shrink a bit.
** Mentioned before, a lot of people using black powder in rifles for single-shots don't resize since the bullet has to sit right on top of the powder. For match use, many don't crimp, either.