Subsonic supressed 5.56/.223

**Gerhard68** · 19-11-2018, 15:11

Hi there.

I started reading up on shooting subsonic rounds on a suppressed AR 15 chambered in 5.56/.223 and basically what i have found is that its really difficult to have it reliably cycle the subsonic ammo.

1. Is there anyone here with a little more personal experience on the subject?

2. will an adjustable gas block solve the cycling issues?

3. is it easy to adjust the gas block for the different ammo?

very interested to know if it can be done with minimal modification if at all possible.

**StanCT** · 19-11-2018, 15:24

Please search the forum for previous threads related to some of your questions.

I seem to recall reading previous discussions, a while back, but not the details.

**A-R** · 19-11-2018, 21:00

The best way to do it is to get a 22LR conversion kit for your AR. Not sure if it will cycle with subsonic ammo, but functioning will be much better than with down-loaded 223.

**The Beast** · 19-11-2018, 21:33

Originally Posted by A-R

The best way to do it is to get a 22LR conversion kit for your AR. Not sure if it will cycle with subsonic ammo, but functioning will be much better than with down-loaded 223.

Good advice. 5.56 subsonics would probably be 70gn at under 1000fps. .22LR can be had off the shelf 40gn at under 1000fps.
This is a good reason to buy another gun.
I have subs for ma 15-22 with a suppressor. It is surprisingly quiet. Not bolt action quite but good enough

**curious george** · 19-11-2018, 22:12

Sort off related and posted today.

**Gerhard68** · 20-11-2018, 07:57

is a 70gr .223 at under 1000 fps not much better than a 40g .22 in terms of actual firepower,penetration and distance?

**Sean Murphy** · 20-11-2018, 08:14

The speed of sound is around 1125fps in sea level dry air at 20deg C, so you can come up a bit over 1000fps. Most 22lr subsonic ammo is loaded at around 1040fps to be safely below sound, allowing for temperature and pressure variations.

Very few standard semi autos will reliable cycle with subsonic ammo. Even if you are happy to cycle manually you still have other complications like fowling the gas tube with filler material, as most such loads require the presence of a filler to keep powder ignition consistent.

**Quicksilver_WP** · 20-11-2018, 08:27

Just buy a 300BLK upper

**Gerhard68** · 20-11-2018, 14:49

Originally Posted by Sean Murphy

The speed of sound is around 1125fps in sea level dry air at 20deg C, so you can come up a bit over 1000fps. Most 22lr subsonic ammo is loaded at around 1040fps to be safely below sound, allowing for temperature and pressure variations.

Very few standard semi autos will reliable cycle with subsonic ammo. Even if you are happy to cycle manually you still have other complications like fowling the gas tube with filler material, as most such loads require the presence of a filler to keep powder ignition consistent.

regarding the filler. I've seen a youtube video where the guy uses teased cotton to fill the cartridge but obviously, its the internet so, take it with a pinch of salt.

Originally Posted by Quicksilver_WP

Just buy a 300BLK upper

LOL.... You must have a lot of free money, no kids and no wife constantly gauging the thickness and weight of your wallet - saying that with a smiley face and all.

If you want to buy a 300BLK upper you might as well buy a 300BLK Rifle, price diff shouldn't be that much and I would assume you need to go through whole FA license process for the upper also.

but that's beside the question guys. I already payed for my AR15 .223/5.56. I know that the .22 and 300BLK is better for subsonic suppressed. my question was regarding suppressing and cycling subsonic .223/5.56 ammo in a semi-auto AR15

my question is if anyone on forum have found a way to successfully and safely cycle subsonic's in an AR15 chambered in .223/5.56.

in anycase thank you for the feedback so far

**The Beast** · 20-11-2018, 20:52

Originally Posted by Gerhard68

regarding the filler. I've seen a youtube video where the guy uses teased cotton to fill the cartridge but obviously, its the internet so, take it with a pinch of salt.

LOL.... You must have a lot of free money, no kids and no wife constantly gauging the thickness and weight of your wallet - saying that with a smiley face and all.

If you want to buy a 300BLK upper you might as well buy a 300BLK Rifle, price diff shouldn't be that much and I would assume you need to go through whole FA license process for the upper also.

but that's beside the question guys. I already payed for my AR15 .223/5.56. I know that the .22 and 300BLK is better for subsonic suppressed. my question was regarding suppressing and cycling subsonic .223/5.56 ammo in a semi-auto AR15

my question is if anyone on forum have found a way to successfully and safely cycle subsonic's in an AR15 chambered in .223/5.56.

in anycase thank you for the feedback so far

The reason that you are not getting much on this is because there are cheap better alternatives.
Reloading subs for a 300BLK that is designed to cycle with subsonic loads is a challenge with SA available powders. Trying to do the same with a caliber that wasn't designed with that in mind will be challenging.