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Thread: An afternoon with a 9mm J frame notes

  1. #11
    Site Supporter ccmdfd's Avatar
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    Feb 2011
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    Quote Originally Posted by Jim Watson View Post
    Has anybody tried having the chambers honed? A common procedure on competition nine-shooters.

    There was a 940 around here that had been cut for 9x23 - .38 Super, still usable with clipped 9mm P that the seller said extracted freely.
    Wow.

    9X23 out of a J frame! That has to be a hoot to shoot.

  2. #12
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    Quote Originally Posted by john c View Post
    Great write up. Thank you.

    Iím unfamiliar with the concept of trailing edge failure. If itís not too much trouble, would you mind explaining to some of the slower students in the class?


    Sent from my iPhone using Tapatalk
    The common 9mm chamber has a square shoulder at the stop surface where the case mouth rests to provide correct headspacing.

    When lead cast bullets are used, the bullet base begins to upset before leaving the case mouth, such that the bullet base is scraped in exiting the case.

    Accumulation of these lead deposits causes in hard cylinder rotation because ammunition does not fully contact the chamber stop surface, but is is impeded from seating fully due to the lead fouling.

    Breaking the sharp corner of the chamber stop surface to provide a chamfer successfully mitigates against this effect.

  3. #13
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    Quote Originally Posted by Jim Watson View Post
    Has anybody tried having the chambers honed? A common procedure on competition nine-shooters.

    There was a 940 around here that had been cut for 9x23 - .38 Super, still usable with clipped 9mm P that the seller said extracted freely.
    Honing or polishing the chambers reduces adhesion of fired brass to the chamber walls and makes the set-back and "pistoning" situation worse. This had been done to a second 940 I bought off GunBroker, and I fixed it by roughing the chamber walls slightly with a 180 - grit lap when doing the chamber mod. Works fine now.

    Full-pressure 9x23 I would expect to give hard extraction. US .38 Super should be OK. Ruger produced a few .38 Super/9x19mm Service Six revolvers for Columbia and 9x21 for Commercial sale in Italy.

  4. #14
    Site Supporter jandbj's Avatar
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    Sep 2012
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    IIRC, S&W made at least one 940 in 356TSW (aka 9x21.5).

  5. #15

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