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CMJ vs FMJ

Discussion in 'Reloading' started by CaptainXL, Nov 1, 2012.

  1. CaptainXL

    CaptainXL

    321
    2
    Nov 20, 2009
    Illinois
    I have someone that wants to sell some MG CMJ 124 Gr 9mm pretty cheap.

    I have never loaded any CMJ but assume that I can use my favorite 124 Gr FMJ load safely. Am I correct in assuming that I would reload just the same as if they were FMJ?

    What is the difference between CMJ and FMJ? I think that I read somewhere a while back that the base is different. Is the base fully encapsulated?

    What, if any, are the advantages of CMJ compared to FMJ?
     
  2. Boxerglocker

    Boxerglocker Jacks #1 Fan

    6,202
    42
    Mar 6, 2003
    Lynnwood, WA
    CMJ just as you stated fully encapsulated, FMJ has an exposed lead base.

    Advantage of CMJ loads is less smoke and chance of lead exposure.
     

  3. Right now I am using MG bullets exclusively; among them 147 CMJ and 230 CMJ. I have had great performance as for as accuracy, and (with my VV powder), no smoke. I've popped a few of the 230s out of the sandy berm and I think I can buff them out and re-use them. (Just kidding... but except for some minor serrations, they look pretty good.)
     
  4. Colorado4Wheel

    Colorado4Wheel

    14,972
    180
    Nov 2, 2006
    CO
    CMJ don't lead the compensator like FMJ can.
     
  5. shotgunred

    shotgunred local trouble maker

    8,877
    1,089
    Mar 1, 2008
    Washington (the state)
    The indoor range I go to in the winter requires CMJ's.
     
  6. CaptainXL

    CaptainXL

    321
    2
    Nov 20, 2009
    Illinois
    No one has answered my question regarding reloading CMJ.

    Are they loaded the same as FMJ?

    Should/can I use my favorite FMJ loading in CMJ?

    I assume so but want to make sure.
     
  7. F106 Fan

    F106 Fan

    8,053
    283
    Oct 19, 2011
    Like everything else in reloading, the answer is probably 'maybe'.

    I don't load anywhere near max so I would just use the same recipe. If I were truly concerned, I would back the load off a couple of tenths of a grain and work back up.

    I have used some CMJ in 9mm and I don't recall doing anything special.

    Richard
     
  8. Hoser

    Hoser Ninja

    2,368
    54
    May 22, 2002
    Same same.

    You are good to go.

    I load 230 and 115 CMJs with the same powder charge as normal. No difference.
     
  9. CaptainXL

    CaptainXL

    321
    2
    Nov 20, 2009
    Illinois

    I don't load near max either and therefore will use my normal favorite load and watch for any abnormal signs.

    Thanks for the input.
     
  10. Colorado4Wheel

    Colorado4Wheel

    14,972
    180
    Nov 2, 2006
    CO
    Like Hoser, we have tested the difference between CMJ and FMJ in 9mm. They work the same.