subsonic 223 rounds in AR

[docmagnum357]

Is it possible to tune an AR to cycle with subsonic cast loads? Adjustable gas blocks, lighter spring? Does anyone have any experience with this?

[BK7saum]

I have seen a factory 223 subsonic AR15. I believe it was subsonic only. I dont remember the manufacturer. Seems like you dont gain much over a 22LR, but about 30 grains of bullet weight.

So, yeah, I'd say it's possible if you wanted a dedicated subsonic rifle. I think there is way too much difference in powder burn rates/case volume/pressures between super ammo and subsonic ro run both well (or at all)in the same gun.

[rancher1913]

just put a solvent trap on it and fire regular ammo.

[Garyshome]

how good Does that work?

[rancher1913]

a friend has one and it works really well, you have to tred softly using it as its a very grey area and you could get in trouble using one in public. a legal bought can is much safer and much more legal but for shooting on your own land to keep noise down so your neighbors dont complain it does work. he was shooting a lot and his neighbors kept complaining so he tried one and it helped a lot, he is older and on a fixed income so a legal can was beyond his financial reach.

[kerplode]

Just so we're all on the same page with this solvent trap business...It's not a grey area at all. Unless you have an approved Form 1 in your hot hands, your solvent trap becomes an unregistered suppressor as soon as you puncture the end cap.

If you do this without a Form 1 and you get caught with it in your possession, on your property or otherwise, there will be SIGNIFICANT legal penalties. Far more than the $1000 or so it takes to do it right.

[kerplode]

Re the OP's question, it's possible to make an AR cycle subs, but by the time you increase the port diameter, shorten the gas system, and tune the buffer, you'll end up with a dedicated upper/rifle. You're also shooting a round that has significantly neutered ballistics. It's just not that practical, so most don't mess with it. You can find some direction on the changes on the web if you're really interested in perusing it.

300BO is a much easier option for an AR system that cycles subs.

Or load 223 subs and run the rifle as a straight pull.

[Lloyd Smale]

correct answer. Its not even worth trying unless you want to run your gun manualy. Solvent trap? Still isn't going to keep you from breaking the sound barrier and that's what will account for most of the noise when your running suppressed in a 556. For what your going to invest in time and loading components and gas to run to the range just pick up a 300 bo upper and then its a pretty easy goal. Even if you do get your 556 to run subsonic like kerplode eluded to your power level is not much more then a 22lr. With a 300 your shooting a 200 grain or heavier bullet at 1100 fps. Much harder hitting and will penetrate about any living target stem to stern.
Re the OP's question, it's possible to make an AR cycle subs, but by the time you increase the port diameter, shorten the gas system, and tune the buffer, you'll end up with a dedicated upper/rifle. You're also shooting a round that has significantly neutered ballistics. It's just not that practical, so most don't mess with it. You can find some direction on the changes on the web if you're really interested in perusing it.

300BO is a much easier option for an AR system that cycles subs.

Or load 223 subs and run the rifle as a straight pull.

[Outer Rondacker]

Yes to the on track question asked. Weaker buffer spring. Lighter buffer. Clean gas tube. Your ammo must be around 1000 FPS or more.

[docmagnum357]

Kinda what I figured.

Looks like a LEGAL suppressor is in the future. If it comes to a dedicated upper, be kind of stupid NOT to go with 300 BO. Shorter learning curve, too. been loading magnum pistol ammo for 35 years. Think I got that one figured out.

Any of you who shoot 300 BLK would you build a pistol with a brace, or go with a barrel swap on a regular AR? I have 2, can't use both at once. Best I understand you don't gain much with a barrel longer than 10-11 inches in blk

[kerplode]

300BO is definitely most efficient in shorter barrels. I think a 8-10" on a braced pistol lower is probably the hot ticket.

16" isn't too bad, though, and saves you from getting another lower. But yeah, you just don't really gain anything in performance from those extra 7" like you would from a more conventional rifle cartridge.

If you're dipping your toe into NFA to get a suppressor, you could also SBR one of your existing lowers on a Form1 and use it for a shorty blackout upper in addition to its existing configuration. $200 and some time, but you get to use a proper stock and don't have to deal with the ATF and their ever-changing position on braces.

[dbosman]

Western Powder publishes tested subsonic recipes for 300 Blackout and .458 SOCOM.
Since there are uppers for both, unless one already had an AR to spare, .223 seems to me, just an interesting project.

[docmagnum357]

yeah, kinda what I have decided. I can build a great, light weight, short, braced pistol and have everything I need. Put a red dot on it, be ready to go.

[TaylorS]

Making a 300BO upper would be best loading sub ammo for the 300BO is simple I’ve run it with a 16” and a 10-1/2” barrel and both barrels like it very well. That said if you are wanting a can on it you can do that with standard velocity 223 rounds and it’ll work just fine in a can and drastically reduce the noise... so I’ve heard. Also can do some reduced loads with it without modifying the gun, just make it so it’s just enough to make the rifle cycle like it should.


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[Conditor22]

300 BO subsonic 247 grn. in a single shot through a can is a blast.

No hearing protection required and you can't get "trigger happy" and eat up ammo in a hurry.

You get to savor each shot :)