I will not be shooting any 405gr moving at 2100 fps lol
probably a good idea!
(if you could even get that from a pistol, I wouldn't want to shoot it)
I have shot 400gr @2100fps from a rifle and tis about all the recoil I am willing to endure.
I have a 14" .45-70 barrel on an old Contender frame (not the G2) and I am rather fond of it. I shoot a 400gr cast slug a couple grains of powder below the old Lyman factory duplication load. I'm not concerned with stretching the frame, and so far the cheap ($35) red dot I put on it has survived a couple hundred rounds over a decade. I'm not worried about making the .45-70 a magnum, not in that gun any way, first of all, the Contender is generally classed as the "Tier I" gun, the same strength class as the Trapdoor Springfield. And second, its a PISTOL, with a 14" barrel, so you're not going to get rifle speeds no matter what.
And, a few feet per second either way doesn't matter, the big bullet doesn't turn into a wimp if it goes a little slower, and doesn't shoot laser beam flat if it goes a little faster.
Recoil, is something else. Very individual thing. My gun wears Pachmayr rubber, which has a good grip and feel, for me. I find the recoil on the heavy side of "stout", but not as vicious as the whip with a 10" octagon .44 Mag barrel (really light barrel, compared to the 14" heavy barrel .45-70).
On the other hand, thinking you know what your doing and then doing it can be different things, until some experience teaches you. Friend of mine, not terribly experienced watched me shooting the .45-70, and wanted to try it. He thought he knew, but it wasn't until after we got the bleeding stopped that he
really knew.
He said he had locked his wrists, but didn't think to tighten his elbows. The red dot sight wacked him smartly near the bridge of his nose!!! He DID hit the target. And, after we got the bleeding stopped and the laughing under control, he asked for another shot!!! (Thank you sir! May I have another? )
He did much better that time, ringing the steel we were shooting and not letting the gun get away from him.
I really like mine, its a (large) handgun, capable of one precise powerful shot at a time. And probably more accurate than I am.
I would avoid any and all of the "upgraded" factory ammo for the .45-70 Contender. Sticking to the black powder velocity stuff or equivalent handloads still delivers a very useful and useable result.
I avoided the Contender for decades, after all, it was "only a single shot". Then, one day I tried the trigger on one at a show, and later another at a shop, and realized I had been missing out on a "shootin' machine!" Not a combat gun, nor a personal defense gun, but an absolutely wonderful shooting gun, one that tested you to be your best, and delivered handsomely when you did.
I found them to be a ..little bit..addicting. I have barrels for .22LR, .22 Hornet, .222Rem, 9mm Luger, .357, 44Mag, ,45Colt/.410, .45Win Mag .30-30 and .45-70. I hope you get the joy from yours that mine have given me.