But I think C. Cliff is a little too dogmatic about those barrel specs.
Ken Waters slugged a number of barrels and found:
Real Winchester 1892 = .428"
Real Winchester 1873 = .429"
Euroarms repro 1873 = .4265"
Colt New Service = .4275"
Load for what you have, not what somebody says you should have.
My relined 1892 is .428" and I would shoot .429" bullets in it if all my brass were thin Winchesters. But I have enough that I get by with .428" when I can find them, otherwise a brand listed at .427" but miking .4275".
Clyde Williamsons book The Winchester Lever Legacy showed a .429 groove diameter for the 92 carbine example they had for working loads up. The older Lyman loading manual I have shows .432" groove diameter in their example. Assuming groove diameters in old Winchesters isn't a good idea. Slugging or miking them is the only way to really know much.
I agree that shooting 44 mags in a 44-40 chamber is a really bad idea with gun wrecking potential. Maybe a case wouldn't rupture, and maybe it could. Not a smart gamble in any way shape or form.