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Q. about subsonic ammo with a PDW?

M

Magnum50

Elite
Hello,
Suppressor and subsonic ammo noob here. I don't have a suppressor for my DD PDW .300 Blackout but I was reading up on it. And believe I read that that particular weapon system, even without a suppressor is made for subsonic rounds to keep the noise level down. Am I reading that right? Should I be using subsonic ammo in this PDW?

"The 7 inch 300 Blackout Cold Hammer Forged barrel keeps subsonic loads subsonic and provides great ballistics for a shorter barrel."

A bonus question... just because I'm trying to learn and understand.

I have a Hellcat Pro and just bought and replaced the stock barrel with the treaded barrel they offer. Just received my tax stamp last week for my suppressor for it. (BTW 5 weeks it took compared to 18 months for my first one 5 years ago, lol.) I got 2 different types of subsonic ammo for it. A box of Freedom Munitions HUSH 147 gr RN and ammo Incorporated stelTH 165 gr TMC.

My question: so 147 grain is lighter then 165 grain, so the 147 would have a faster velocity, but the heavier 165 would be more quiet. Is that how it works? and what does RN and TMC mean? I usually see and know FMJ (ball) and HP (more for defense). Right?

Going to range Wednesday to test some subsonic ammo for the first time. Had my 1st supressor 5 years ago for my Sig MPX but never used subsonic ammo in it, same with my SOCUM Suppressor for my AR15. Never used subsonic... so first time testing. I'm excited. lol

THANKS.
 
and yet another question/observation... is all subsonic ammo ball ammo. Looking at them all don't see any hollow point type subsonic ammo. Wouldn't you want HP subsonic ammo for your defense gun with a suppressor, like I use my Sig MPX for. it hangs locked and loaded behind my bedroom door. Just wondering? Thx.
 
.300blk subsonic ammo can have cycling issues in certain firearms not equipped with a suppressor because of the lack of back pressure to fully cycle the bolt. A suppressor is recommended while using .300blk subsonic ammo. I have numerous .300blk firearms in the safe and I reload my own .300blk rounds.

I don't think you will get any noticeable sound suppression between 147gr vs 165gr 9mm ammo as they are both subsonic rounds and the decibel difference between subsonic rounds is negligible in my experience. The sonic boom from supersonic rounds is a one part of the sound you hear from a gunshot and the explosion of the gunpowder is the other part. A suppressor muffles the explosion but cannot muffle the supersonic crack so two subsonic rounds of the same caliber with different grain weights will have a very similar sound caused by the explosion of the powder.
 
Two things make noise when you fire a round. One is gas discharging behind the bullet. Suppressors reduce noise by capturing and retarding the gas. The second thing that makes noise is the sonic crack of the bullet breaking the sound barrier. Subsonic rounds traveling below the speed of sound don't make that crack. The 9mm 147 grain subsonic round was first developed to work in suppressed submachineguns like the HK MP5. MOST quality subsonic HP ammo will run in quality guns, but it depends on what your gun likes. Test it in your gun before depending upon it.
 
Magnum50 said:
Hello,
Suppressor and subsonic ammo noob here. I don't have a suppressor for my DD PDW .300 Blackout but I was reading up on it. And believe I read that that particular weapon system, even without a suppressor is made for subsonic rounds to keep the noise level down. Am I reading that right? Should I be using subsonic ammo in this PDW?

"The 7 inch 300 Blackout Cold Hammer Forged barrel keeps subsonic loads subsonic and provides great ballistics for a shorter barrel."

A bonus question... just because I'm trying to learn and understand.

I have a Hellcat Pro and just bought and replaced the stock barrel with the treaded barrel they offer. Just received my tax stamp last week for my suppressor for it. (BTW 5 weeks it took compared to 18 months for my first one 5 years ago, lol.) I got 2 different types of subsonic ammo for it. A box of Freedom Munitions HUSH 147 gr RN and ammo Incorporated stelTH 165 gr TMC.

My question: so 147 grain is lighter then 165 grain, so the 147 would have a faster velocity, but the heavier 165 would be more quiet. Is that how it works? and what does RN and TMC mean? I usually see and know FMJ (ball) and HP (more for defense). Right?

Going to range Wednesday to test some subsonic ammo for the first time. Had my 1st supressor 5 years ago for my Sig MPX but never used subsonic ammo in it, same with my SOCUM Suppressor for my AR15. Never used subsonic... so first time testing. I'm excited. lol

THANKS.
Click to expand...
10mmLife said:
.300blk subsonic ammo can have cycling issues in certain firearms not equipped with a suppressor because of the lack of back pressure to fully cycle the bolt. A suppressor is recommended while using .300blk subsonic ammo. I have numerous .300blk firearms in the safe and I reload my own .300blk rounds.

I don't think you will get any noticeable sound suppression between 147gr vs 165gr 9mm ammo as they are both subsonic rounds and the decibel difference between subsonic rounds is negligible in my experience. The sonic boom from supersonic rounds is a one part of the sound you hear from a gunshot and the explosion of the gunpowder is the other part. A suppressor muffles the explosion but cannot muffle the supersonic crack so two subsonic rounds of the same caliber with different grain weights will have a very similar sound caused by the explosion of the powder.
Click to expand...
This 👆
10mm said it best 👍👍
 
RN = Round Nose
TMC = Total Metal Coating

HP ammo requires velocity for expansion. Subsonic ammo reduces velocity. I'd guess that cartridge developers realize getting a bullet to expand at very low subsonic velocities is a challenge... Although, Federal HST 147gr 9mm expands quite well...so it is not a universal truth.
 
HayesGreener said:
Two things make noise when you fire a round. One is gas discharging behind the bullet. Suppressors reduce noise by capturing and retarding the gas. The second thing that makes noise is the sonic crack of the bullet breaking the sound barrier. Subsonic rounds traveling below the speed of sound don't make that crack. The 9mm 147 grain subsonic round was first developed to work in suppressed submachineguns like the HK MP5. MOST quality subsonic HP ammo will run in quality guns, but it depends on what your gun likes. Test it in your gun before depending upon it.
Click to expand...
Unless, of course, you run a MP5SD; HK says to only run standard velocity 124gr through it, as its 4” barrel & baffle stack is designed to bleed the velocity off to subsonic before it exits the muzzle.

Subsonic/147gr bullets can cause baffle strikes because they get slowed down too much.

(As I was informed when I got to run a MP5SD; asked if they were subsonic, and was informed of the above)
 
HansGruber said:
Unless, of course, you run a MP5SD; HK says to only run standard velocity 124gr through it, as its 4” barrel & baffle stack is designed to bleed the velocity off to subsonic before it exits the muzzle.

Subsonic/147gr bullets can cause baffle strikes because they get slowed down too much.

(As I was informed when I got to run a MP5SD; asked if they were subsonic, and was informed of the above)
Click to expand...
My team had 16 MP5's in the Navy configuration with threaded on
suppressors and they ran fine with 147 grain subsonics. We avoided the MP5SD with integral suppressor due to maintenance issues, they were fussy.

I miss my MP5.
 
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