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Don't use JHP ammo in a suppressor?

Discussion in 'NFA Firearms and Accessories' started by wally, Mar 30, 2014.

  1. wally

    wally Well-Known Member

    Just picked up my Thompson Machine ISIS-2 and reading through the package insert sheet there is an Installation and Use section that says:

    "The Isis-2 should only be used with factory-loaded non +p FMJ ammunition. DO NOT FIRE HOLLOW POINT AMMUNITION IN YOUR ISIS-2! We recommend Alabama Ammo Special-K or similar loadings."

    First I've heard of not using JHP, not an issue as with the volume I shoot, I buy what's cheapest and I've never seen JHP for less than FMJ, and +p makes no sense if you are wanting to be quiet and hopefully subsonic. I've also never heard of "Alabama Ammo".

    Maybe JHP has a lot of yaw on exiting the barrel? Some stop action shots I've seen of bullets leaving the barrel have left me wondering how baffle trikes don't happen.
  2. Theohazard

    Theohazard Well-Known Member

    It's fine to shoot JHPs as long as the suppressor doesn't use wipes that the bullet passes through (and I'm pretty sure your Thompson doesn't). The vast majority of suppressors on the market today don't use wipes and therefore the bullet doesn't actually touch anything, so it's completely fine to use JHPs.

    I think the warnings against using JHPs come from the fact that you're more likely to have a jacket separation with a JHP than with a FMJ, and if that happens inside the suppressor the baffles could be damaged. Also, at any given weight a JHP is going to be longer than a FMJ due to the hollow cavity, so you're more likely to have stabilization issues with JHPs.

    So if you want to use JHPs in a suppressor just make sure the jacket isn't coming off in flight and that the bullet isn't keyholing, and you'll be fine.
  3. Arizona_Mike

    Arizona_Mike Well-Known Member

    In fact, many people prefer to shoot JHP because they have no lead exposed to hot gasses and thus no lead vapor to plate out in the suppressor.

  4. wally

    wally Well-Known Member

    I'm just reporting what was in the package insert. I think Theohazard may have it, as Thompson Machine is one of the few still making suppressors with wipes -- their super small and light Poseidon models.

    The package insert may just be a cut and paste job with the suppressor name plugged in.

    The high speed videos I'd referred to showed serious yaw a few inches beyond the barrel and appeared to stabilize a few inches beyond that. Did leave me wondering how'd they'd pass through a can.

    Since I can take it apart, it'll be interesting to look at it after shooting Berry's plated (100% copper coverage, vs. "normal" FMJ vs. hard cast lead as time goes by.

    Going to take some "virgin" photos today and hope to get out and try it tomorrow.

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