[Jabames]

Can a .45-70 be re-barreled to a .450 NE 3&1/4" or a .450/400 NE 3"

 

[Jabames]

oops I mean rechambered

 

[Rangr44]

FWIW, rechambering is worthless, if action cannot handle the larger/wider/longer, more intense cartridge - not to mention one's shoulder.............................

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[Shawn Crea]

Rangr44, that wasn't very helpful, and recoil wasn't even asked about.

Jabames,
It depends on the rifle you are contemplating for the conversion. A Springfield 45-70, very likely not. A Ruger #1 or Browning 1885, maybe. The 450's have a rim diameter of 0.624", the 45-70 a rim dia of 0.608". Case base on the 450's is 0.545" dia, on the 45-70, 0.5056" dia. Rim thickness on the 450's is 0.042". On the 45-70, 0.070". That's the headspace bugaboo. I'd be talking to a gunsmith.