Copper cased .45-70? Inside primed?
Oh, you mean one of these.
I've got one of those around here in .45 S&W, too...
The copper-cased .45-70 round was adopted for a very logical reason -- deep brass drawing was still in its infancy, and still giving the military a lot of trouble. As a stop-gap measure it was decided to stick with the copper until the brass draw method was perfected a few years later.
Commercially the deep brass draw method was used a number of years before the military used it, but it was very problematic. The only saving grace was that commercial ammo didn't tend to sit around for nearly as long as military ammo.
And, early on, the commercial companies didn't necessarily use deep brass drawing, they spin drew them, a much slower and less precise method that leaves you with thicker case walls.
In fact, I'm pretty sure that's how Ballard's "Everlast" cases were made. There is no way that they could have been deep drawn using the technology and methods of the day, not with case walls that thick.
As for not knowing anyone using copper cased ammo other than the US military, the commercial loaders in this country churned out BILLIONS of rounds of copper-cased .22s all the way up to, and possibly past, World War II.
The priming method, in this case the type developed by Col. Steven Benet, was because copper wasn't strong enough to support a punched through center fire primer.
The British, of course, addressed both problems in a different way -- to deal with the fact that they couldn't draw brass, they used a rolled brass foil/cardboard sandwich for the bodies on the .577 and .577/.450 cartridges. The body was rolled, and then inserted into a punched brass cup. An iron washer was placed on the back of the cup, and a hollow rivet was run through all three pieces, holding the whole thing together. The primer was then set into the hollow rivet, making it look not unlike a shotshell.
Contrary to popular belief, the extraction problems weren't due solely to the fact that the cases were relatively soft copper. It had lot more to do with the design of the extractor (it bore on only a very small part of the rim), it was a black powder gun, so the chamber fouled, and when fired quickly, the gun heated up.
The British experienced many of the same problems with their Martini-Henry's and they were shooting the composition cartridges I've described above.
As for the Colt Lightning, the rounds that I shot were very light reloads to take into account that the rifle is old and valuable. So, no extraction problems.