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jackstrawIII · December 29, 2019, 02:07 PM

Hey guys,

I have a CZ 550 in 6.5x55 that I want to convert to 9x57 Mauser. Here's the catch, I don't want to re-barrel or set the barrel back at all. Hoping to just rebore and rechamber.

Would it be as simple as:
- Have JES Rebore/rerifle the barrel to .358 (so I can use standard 35 caliber bullets)
- Reaming the chamber out with a 9x57 reamer

Is that all it would take? I realize the rim diameter for the x57 case is a just a hair smaller than the x55 case... is that a huge problem? It's hard to tell if the 9x57 reamer would "clean up" the existing x55 chamber.

I know the simple solution is to re-barrel, but I'd prefer not to do that. Want to keep the gun as unchanged as possible.

Ps. If that won't work, is there a somewhat common 35 caliber wildcat based on the x55 case that I could use? Couldn't find one... but maybe it's out there. Thanks.

December 29, 2019, 02:07 PM	#1
jackstrawIII Senior Member Join Date: July 20, 2016 Location: Upstate NY. Posts: 901	Reboring 6.5x55 to 9x57 Mauser Hey guys, I have a CZ 550 in 6.5x55 that I want to convert to 9x57 Mauser. Here's the catch, I don't want to re-barrel or set the barrel back at all. Hoping to just rebore and rechamber. Would it be as simple as: - Have JES Rebore/rerifle the barrel to .358 (so I can use standard 35 caliber bullets) - Reaming the chamber out with a 9x57 reamer Is that all it would take? I realize the rim diameter for the x57 case is a just a hair smaller than the x55 case... is that a huge problem? It's hard to tell if the 9x57 reamer would "clean up" the existing x55 chamber. I know the simple solution is to re-barrel, but I'd prefer not to do that. Want to keep the gun as unchanged as possible. Ps. If that won't work, is there a somewhat common 35 caliber wildcat based on the x55 case that I could use? Couldn't find one... but maybe it's out there. Thanks. __________________ In God we trust. Last edited by jackstrawIII; December 29, 2019 at 04:42 PM.