Possibly a dumb question but....

No, not really.

You could possibly neck size enough to fit a bullet.
And possibly crimp enough to be safe in a lever-action.
But not while using the press ram depth stop or cam over feature to get consistent results each round.

But only if your press & dies allow backing out .45 Colt dies far enough to do all that without falling out on your foot and hurting it.

The thing to remember is, if one set of dies could correctly and safely load .45 Colt & 45-70?

They wouldn't bother to make two different caliber die sets.

rc

The bullet diameter for 45-70 is .458. Bullet diameter for .45 Colt is .451/.452. They are really of two different worlds. You would at least need a 45-70 expander die to size the cases properly for a .458 diameter bullet.

If your expander die is too small (.45 Colt) you will crush the bullet trying to seat it. Soft JHP will get pretty mashed and you might even buckle some brass.

Just get a set of 45-70 dies and be done with it.

Dan

No.

And don't go the other way either.

45 colt, 454, and 460 mag all work in a 460 mag gun just like 38/357. 45/454/460 and 45 acp are all 0.452" diameter, although some old 45 colts were 0.454".

45-70 is also a tapered case. 45LC.....straight wall.

The 45 colt size die would size the 45-70 case mouth down tight enough to hold the 45 colt bullet. But the biggest problem you'll hit is when you touch that round off in the 45-70 the bullet will be about bore diameter and unless you have a real smooth bore and grooves and a good throat with a superior lube on that bullet it's going to lead the snot out of that 45-70 barrel.
I do from time to time use a 45 colt size die to give good neck tension to bore diameter paper patch rounds in the 45-70.

Totally different cartridges and components. About the only commonality between the two would be the 45 in the name.