One of the 'beauties' of a single shot .45-70 is that it is not necessary to crimp in any fashion. There is no magazine spring, nor pressure on the front of the cartridge attempting to push the bullet back.
The ONLY reason you might find it necessary to crimp for a single shot is with a load that needs a bit more resistance on the bullet release at the git for consistent and complete burn. Now, if I had a magazine gun in the closet next to my Handi, and wanted to keep the bullets in place, a crimp would be appropriate.
The 405 Remington is a decent enough bullet, and if you prefer a jacketed bullet to cast, and want to shoot more, it's about the most reasonably priced bullet out there, and yes, they shoot just fine.
With a bullet seated out farther in a long throated rifle, I'd just run it into the seating die enough to get rid of the 'bell' at the case mouth and call it good. Note that you're increasing the internal capacity doing that, and it may change the way the load performs, so some charge adjustment may be needed to get back the published performance.
The Marlin Cowboy gun I had would not feed the Remington 405 unless it was seated below the front driving band, leaving the case mouth hanging in the air. In THAT rifle, I had to trim the cases well below the 'trim-to' length, and crimp into the jacket as far forward as I could. Started shooting the 350 Hornady in that rifle, and got rid of all the hassle, more velocity, and got a more stoutly constructed bullet. That rifle is the only .45-70 lever gun I've loaded for, and others may handle the load just fine at published COAL. What was happening in that rifle is that the round would exit the tube, but was long enough that the bullet, while the cartridge was on the lift lever, was hanging up on the receiver, and I'd have to disassemble the rifle to clear the jam. Bad JuJu.....
With the caveat that I've not personally shot a game animal with the bullet, I've heard that they'll kill anything on this continent just fine with a proper hit. A poorly hit animal dies ugly no matter what it's hit with. I don't believe that I'd be out trying to put Dumbo or M'Bogo down with one on purpose, but if it's what I had in my rifle on a moose hunt and had to argue with Mr. Griz on the trail, I'd perforate 'im in a heart beat with it.