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Discussion Starter · #1 ·
I have an AR in 9mm that I enjoy shooting. But the suppressor for it arrived, and I found that the 16" 9mm barrel makes my 124 and 147 grain subsonic loads go supersonic. Every time.

I need a shorter barrel.

Does anyone have a suppressed 10.5" 9mm AR that can confirm subsonic ammo stays subsonic with it? I suspect it will, but would like a confirmation before I lay out the cash.
 

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Don't have a suppressed in pistol caliber but I can tell you that a shorter barrel means less time for the round to spin up meaning less speed thus further under the sound barrier.
 

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Discussion Starter · #4 ·
I think I will go with an 8.5" barrel. My 124 grain loads *should* stay subsonic with 8.5.
 

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based on that chart you'll need to stay at 5" or less to be subsonic, unless you go with 147 gr only then you might be able to go 8". but that chart is not suppressed. however i dont think that a suppressor decreases velocity as it increase pressure... idk i could be wrong.

that cmmg banshee is really cool, I would love something like that.
 

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maybe consider subsonic ammo if you really want it quiet? just a thought. idk i would probably shoot regular 9mm most of the time even if it is alittle louder, and then have a few boxes of sub sonic loads for when you really want to be sneaky :cool:
 

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Discussion Starter · #8 ·
maybe consider subsonic ammo if you really want it quiet? just a thought. idk i would probably shoot regular 9mm most of the time even if it is alittle louder, and then have a few boxes of sub sonic loads for when you really want to be sneaky :cool:
I load both my 124 and 147 grain to be subsonic, but specifically to me subsonic and still cycle my sub machine gun.

You may be on the right track, that I’ll just be shooting whatever ammo out of this I have on hand and accepting it if there’s a sonic crack. But, I have a loaner 10.5” upper lined up to test with.

I went down to the AR store this afternoon and looked at barreled uppers, and 8.5” is awefully short. I wouldn’t want to go any shorter than that, and would prefer to stick with 10.5” as a minimum
 

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Sig MPX SBR with 8" barrel, runs 147 grain 9mm suppressed fine and quiet.

So do the 8.9" MP5s.
 
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Discussion Starter · #10 ·
Update on this.
The 10.5" barrel is marginal. It kept one of my 147 loads subsonic, but not both of them. 124's were all supersonic. A guy at the range had a 4" or 4.5" barrel, which certainly kept them subsonic but I definitely don't want to go that short. I need to find someone with an 8.5" barrel to test on before I do anything.
 
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