Muzzle break thread sizes

FWAddit

February 23, 2012 12:00

I recently acquired a P17 Enfield with a .270 barrel fitted with a muzzle brake labeled Johnson-Gartman. I assume the whole rifle was put together by Johnson-Gartman Custom Guns some years ago.

I hate the muzzle blast and don't mind .270-level recoil, but with the single load I have tested, the rifle shoots better with the brake in place than without it. It occurred to me that the Browning/Winchester BOSS CR (conventional recoil) accessory might fit onto the threaded shank for the Johnson-Gartman and increase my options for matching barrel harmonics to selected loads. The shank measures .605 in diameter; I don't have a thread gauge to determine TPI.

Anyone know if it will fit?

If not, where can I find a thread protector?

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  FWAddit

  February 23, 2012 12:05

  Oops, I notice I misspelled "muzzle brake" in the title. [:I]

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  burpfire

  February 23, 2012 14:16

  you will need to know thread pitch! just because the barrel diameter is the same, it could have been threaded with any kind of pitch. i have run into thread pitches where you just shake your head and wonder why! even had a thread pitch that no one could be 100% sure what it was, so had to cut the barrel and re-thread. take your muzzle break to a gunsmith or a fabrication shop. they should be able to help.

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  v35

  February 24, 2012 16:00

  Better to cut a new thread to match the barrel thread than to try and duplicate the muzzle brake thread for the new brake from the old brake.
  You should strive for the tightest fit that can be assembled by hand.
  Any machinist has a a set of thread pitch gages.

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