Subsonic 9mm ammunition

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Subsonic 9mm ammunition

Post by iron369 » Tue Feb 16, 2016 8:27 pm

I've been looking in to different 9mm ammunition since I'm building a 9mm sbr that I'll be running suppressed. The magic number for velocity seems to be 1150fps. I know different variables contribute to the actual speeed of sound but for arguments sake, let's go with 1150. I've seen a lot of 147gr that's 890fps. Supposedly subsonic. The same manufacturers offer "subsonic" 9mm that is 165 grain and 700fps and substantially moe expensive. I understand the projectile price making some cost difference. What I don't understand is why some 9mm that is not marked as subsonic but far below the sonic threshold. Both rounds are round nose fmj. Can someone explain to me what is going on?
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Re: Subsonic 9mm ammunition

Post by Niceguy » Tue Feb 16, 2016 8:40 pm

Everything 147gr or heavier I've shot has been SUPER quiet out of all my pistols, and pretty close to the same in my 16" barrel Sub2k.

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Re: Subsonic 9mm ammunition

Post by Frailer » Tue Feb 16, 2016 8:49 pm

Factory 147 grain ammo has been around for a long time, and it has always been subsonic, even in "+P" loadings.

My assumption is that when the suppressor craze took off some manufacturers saw a marketing opportunity and slapped "subsonic" (along with a higher price tag) on the box.

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Re: Subsonic 9mm ammunition

Post by Niceguy » Tue Feb 16, 2016 9:01 pm

Correct... Fed HST 147gr +P's are even pretty quiet out of the 16" Sub also.

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Re: Subsonic 9mm ammunition

Post by iron369 » Tue Feb 16, 2016 9:38 pm

So then the 165gr wouldn't be quieter?
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Re: Subsonic 9mm ammunition

Post by Niceguy » Tue Feb 16, 2016 9:52 pm

It is in my pistols. I ran out of it before I bought the Sub2k and haven't ordered anymore yet. I would imagine an even bigger difference in it than in the pistols but that's just a guess.

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Re: Subsonic 9mm ammunition

Post by Whootsinator » Tue Feb 16, 2016 9:53 pm

Once a bullet is subsonic weight alone SHOULDN'T affect the sound as far as I can think it through. Subsonic is subsonic, and won't produce a supersonic crack. MAYBE a particular line of specialty subsonic ammo would have powder optimized for as complete combustion as possible, but I don't know how much that would matter. I'm not a suppressor SME, I don't even own any, but my guess is that there would be very little difference between standard 147gr 9mm and specialty subsonic 9mm, especially out of a rifle.
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Re: Subsonic 9mm ammunition

Post by Niceguy » Tue Feb 16, 2016 9:58 pm

The slower .22lr's like the quiets or super colibris are noticeably quieter than say a CCI Standard that is close to the upper edge of staying subsonic out of the rifles. I have no scientific research behind this. Just my ears while shooting my toys...haha

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Re: Subsonic 9mm ammunition

Post by Whootsinator » Tue Feb 16, 2016 10:03 pm

Can't argue with what you really experience in person.
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Re: Subsonic 9mm ammunition

Post by Dave1965 » Tue Feb 16, 2016 11:33 pm

Whootsinator wrote:Can't argue with what you really experience in person.

never stopped you before :shock:

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Re: Subsonic 9mm ammunition

Post by Frailer » Tue Feb 16, 2016 11:38 pm

Niceguy wrote:The slower .22lr's like the quiets or super colibris are noticeably quieter than say a CCI Standard that is close to the upper edge of staying subsonic out of the rifles. I have no scientific research behind this. Just my ears while shooting my toys...haha
Apples and tangerines. Those are quieter because they are using less propellant--a lot less, which is why they don't cycle the action of semiautos. One reason I don't own a .22 suppressor is I don't need one. CCI CBs out of my long-barreled Henry are Hollywood assassin quiet.

The purpose of using subsonic ammunition is to get rid of the crack caused when the bullet breaks the "sound barrier." A suppressor does nothing to mitigate this (since it happens after the bullet leaves the muzzle), so if you want to be as quiet as possible you have to keep the bullet moving slower than the speed of sound (i.e. subsonic).

This threshold varies with air density (which itself varies with altitude and temperature). Basically, the colder it is and the lower your altitude the slower your bullet needs to go. At the temperatures and altitudes most of us are going to be shooting we need to stay under 1100 fps, and ideally under 1000.

I shoot Speer Lawman 9mm almost exclusively (a relatively hot standard pressure load designed to replicate the performance of their Gold Dot rounds), and the published muzzle velocities of their 115, 124, and 147 grain projectiles are As follows:

115 gr
Muzzle Velocity: 1200 fps
Muzzle Energy: 368 ft. lbs.

124 gr
Muzzle Velocity: 1090
Muzzle Energy: 327 ft lbs

147 gr
Muzzle Velocity: 985 fps
Muzzle Energy: 317 ft lbs

As an aside, the drop in "muzzle energy" is the result of energy being a function of the square of the velocity. If we used momentum (or "power factor") instead, we'd see higher figures for the heavier bullets, since it is the result of mass times velocity. Bottom line, these loads have roughly the same "oomph."

The 147 grain bullet is no-fooling subsonic, yet it will still cycle a semi-auto firearm reliably. There will be no sonic crack. The only way to make it quieter is to reduce the amount of expanding gas the suppressor has to handle. Problem is, that means "bunny fart" loads that might not cycle the action reliably.

In the case of the specific loads mentioned in the OP, the 165 grain load probably will be quieter, not because it's slower, but because it's a weak load, with a "power factor" of only 115 and 179 ft lbs of energy. Bunny farts.
Last edited by Frailer on Tue Feb 16, 2016 11:40 pm, edited 1 time in total.

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Re: Subsonic 9mm ammunition

Post by son of liberty » Tue Feb 16, 2016 11:39 pm

Niceguy wrote:The slower .22lr's like the quiets or super colibris are noticeably quieter than say a CCI Standard that is close to the upper edge of staying subsonic out of the rifles. I have no scientific research behind this. Just my ears while shooting my toys...haha
I have experianced simular effects, best i can tell its a gas/ pressure thing. More pressure/gas in the same size muffler. Push a standard v8 through a flowmaster and shove a top fuel v8 through the same muffler. Thats my redneck idea of why but again no science to back it up.
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Re: Subsonic 9mm ammunition

Post by Frailer » Tue Feb 16, 2016 11:42 pm

son of liberty wrote:
Niceguy wrote:The slower .22lr's like the quiets or super colibris are noticeably quieter than say a CCI Standard that is close to the upper edge of staying subsonic out of the rifles. I have no scientific research behind this. Just my ears while shooting my toys...haha
I have experianced simular effects, best i can tell its a gas/ pressure thing. More pressure/gas in the same size muffler. Push a standard v8 through a flowmaster and shove a top fuel v8 through the same muffler. Thats my redneck idea of why but again no science to back it up.
You are exactly right.

Everything's a compromise. Sure, you can make ammo that's *really* quiet, but it won't knock over a soda can.

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Re: Subsonic 9mm ammunition

Post by Niceguy » Tue Feb 16, 2016 11:52 pm

Yep. I agree with both. My response was to his subsonic is subsonic, you can't have more or less subsonic comment. All of the .22's I mentioned are subsonic, yet some are still even a little more quiet than others. Also agree that the super quiet ones are fairly useless. They also make me leary of them not making it out of the barrel in some cases. Like the super colibris.

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Re: Subsonic 9mm ammunition

Post by son of liberty » Wed Feb 17, 2016 12:11 am

iron369 wrote:I've been looking in to different 9mm ammunition since I'm building a 9mm sbr that I'll be running suppressed. The magic number for velocity seems to be 1150fps. I know different variables contribute to the actual speeed of sound but for arguments sake, let's go with 1150. I've seen a lot of 147gr that's 890fps. Supposedly subsonic. The same manufacturers offer "subsonic" 9mm that is 165 grain and 700fps and substantially moe expensive. I understand the projectile price making some cost difference. What I don't understand is why some 9mm that is not marked as subsonic but far below the sonic threshold. Both rounds are round nose fmj. Can someone explain to me what is going on?
Dropping the velocity down low gives a larger margin of error or change insuring that the round is subsonic at any elevation in any conditions at any ammo temp.
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Re: Subsonic 9mm ammunition

Post by Whootsinator » Wed Feb 17, 2016 12:30 am

Niceguy wrote:subsonic is subsonic
My comment was only meant to say that if it's subsonic you won't hear a supersonic crack and that the differences between sub vs sub will be small, especially compared to sub vs super. I could have made it clearer.
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Re: Subsonic 9mm ammunition

Post by Frailer » Wed Feb 17, 2016 12:30 am

FWIW, 900 fps is subsonic at sea level at -120 F.

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