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Thread: Subsonic 9mm troubles in a BRP gun

  1. #1
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    Subsonic 9mm troubles in a BRP gun

    I'm having troubles with 9mm 147g ammo. It finally motivated me to stop lurking and join this forum.

    ANYway, My I'm trying to load something quiet for my 9mm BRP. I test fire vertically into a bucket of sand in the basement. Not the safest perhaps, but it works for me.

    147g/3.6g of TiteGroup ran away. Apparently not enough zip to send the bolt far enough to trip the sear. I bumped the load up to 3.8g, same problem. By this point, the ammo is pretty hot according to the specs I have.

    It COULD be the fact that I'm firing the gun vertically, but I'd rather the angle not be a critical factor in reliability

  2. #2
    Registered User MPA guy's Avatar
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    I typically only load 147's at 3.3 or 3.4 gr of titegroup.

    It cycles heavy slowfire open bolts, uzi, scorpion, and anything else I feed it to.

    I wonder if you don't have something else going on besides ammo power.

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    Cool, that gives me something to go on. This is my first time messing with heavy 9mm bullets, so I'm trying to be cautious.

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    Spring pressure on your bolt is also a factor to consider

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    Registered User K2's Avatar
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    Welcome Starvingboy,

    All guns have their favorite loads that make them run reliably. Depending on how well aligned/worn-in/recoil spring condition might be, some loads that work well in one gun will not cycle another gun.

    I do know that many of my supressed 9's will run on 3.6gr TG with 147RNx1.15 oal. I know of many guns at our monthly matches that will not run unless fed with 3.8gr TG 147RNx1.15oal.

    Note I mention the OAL of the cartridge. Heavy 9x19 are sensitive to OAL. Shorter means more pressure rather quickly. I also run 160RN in the 9X19 and it is very sensitive to OAL when it comes to pressures.

    It is helpful if we know the bullet being used and OAL of the loaded cartridge. For instance, if your 147 is a HP and set at 1.16 OAL, the pressure is much lower than a 147RN set to 1.14 OAL.

    Good luck with your loads. If your primers are missing after firing the round, the pressure is likely excessive

    K2

  6. #6
    Registered User MPA guy's Avatar
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    I normally run mine 1.100" @ 3.3 gr TG.

    YMMV, FWIW, etc.

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    Thanks for the input guys, I'll keep tweaking. I figured "More Powder" was not the answer, and I was running my OAL at the max length. I was hoping someone had a BRP/Stemple set-up to compare against, but they are apparently not that common (?)

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    You may want to latch onto an extra recoil spring and start slowly clipping it down a 1/4 coil at a time

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    I would highly recommend calling or emailing Brian Poling at BRP Corp. That's one of the best things about these guns is that you can always count on Brian for technical support after the sale. He's a very knowledgeable and willing to help!

  10. #10
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    Try COAL of 1.135-1.145 with 3.5gr of TG
    Chris Hipes
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    Which recoil spring/buffer are you running? If you look at your owner's manual for the BRP, there are different configurations for full power vs. reduced loads. I have not tried to run subs in mine yet so I can't advise which combination will work best, but look at the manual and call Brian. He is very helpful and willing to walk you through the proper set up for your ammo.

  12. #12
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    I'm using 147 Extreme plated, 3.6 TG with 1.40 coal
    I use the RF-1 configuration on the BRP STG U9 SF .
    Last edited by strobro32; 03-20-2017 at 09:57 PM. Reason: correction
    If it doesn't splatter, shatter, burst, boing or explode, it's not worth shooting. :)

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    Quote Originally Posted by strobro32 View Post
    I'm using 147 Extreme plated, 3.6 TG with 1.40 coal
    I use the RF-1 configuration on the BRP STG U9 SF .
    That's what I was looking for. I'm running a U45 set up in the 9mm configuration, lightest bolt, standard spring, near as I can tell. So I need either the dedicated 9mm set-up (Been looking for an excuse to buy a Suomi conversion) or trying for a lighter recoil spring. I'll sling an email off to Brian. Every time I call, it ends up burning up an hour or so just BS'ing about guns. I can do that at the creek next month and not get funny looks at the office.

  14. #14
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    3.9g of titegroup get me 930fps on the chrono!! you need more powder to push that bolt back
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