shooting 45-70 in 45-120

[leapfrog]

This is my first post so hopefully this is the correct forum, if not I apologize.
Recently at a gun show I was looking at a sharps 45-120 and the guy asked if I was interested in it and I said not really I have one and was thinking about changing the barrel to 45-70.He said there is no need to do that you can shoot 45-70 in a 45-120 as long as you shoot only lead bullets.
Well this did not sound right to me so I will ask the people here that know what they are talking about.
What damage will be done to the barrel and is it safe?
Thanks in advance.

 

[MilsurpShooter]

As far as I know the only difference between a 45-70 and a 45-120 is the second number. The 70 and the 120 reffers to the powder charge behind the bullet. As far as damage to the rifle, well the thing I would worry about would be the barrel length and would a 70 grain charge manage to get it out of the barrel, past the rifling and out to where you need it to go.

My opinion, might want to wait for someone more qualified then I am though.

 

[Dave Markowitz]

Jay is partly right.

Aside from more powder, the .45-120 has a longer case. The .45-70 case is 2.1" long. The .45-120's is 3.25" long. So, if you shoot .45-70 in a .45-120 chamber, the bullet has a long jump to get to the rifling, similar to what happens when you shoot .22 Short in a .22 LR chamber.

 

[Stickjockey]

Aren't the cases tapered as well? If so, I'd think the differences in case taper/shape would cause pressure concerns, or at least split cases.

 

[Jim Watson]

No, there is no risk or damage unless you shoot so many of the short cases as to "erode" the long chamber.
The only real problem is that you cannot bet on hitting much with a .458" bullet jumping over an inch through a .480" chamber and slamming into the rifling at whatever angle and speed.
The .45x3.25" has a reputation of being hard enough to get to shoot well with the proper brass.