Does anyone know of an AR-15 upper or rifle that will cycle subsonic ammunition?

Welcome to ARFCom

Thanks ! Was wondering if anyone knows of an AR-15 upper  or rifle that will cycle subsonic ammo?

One guy mentioned that in here: https://www.ar15.com/forums/ar-15/Setup-for-reduced-loads-Concept-and-initial-test/4-738347/#i7864556

I don't know of any factory upper or rifle that will do it.

probably need a pistol length gas on a 14" or longer barrel, or an oversized carbine length on a 16 or longer then dick around with everything else. subsonic .223 is just about the same thing as a .22lr so except for a few giggles i dont think people go that route, might as well get a .22 conversion and save on ammo cost

Engel Ballastic Research (sp?)

used to make subsonic 5.56 that was designed to cycle a standard AR action.. It was for Military use supposedly. Used Tungsten bullets in order to be heavy, but still be short enough to stabilize in a 1-7 barrel.

Subsonic 5.56 in an AR isn't very attractive when you can be quieter and cheaper with .22 or significantly more effective with any number of larger subsonic rounds.

I think the only real use is occasional military applications like shooting wild dogs.

.300 using the same mags and bolts makes it even less attractive.

In order to build a rifle that would work you would probably have to limit it to sub-sonic only. If the gas system was designed to work with low power ammo it would not be happy with full power loads.

.22 long rifle, .300 Blackout or 9mm shooting 147's are your only real options.

Ballistically better also.

At that point you might as well be shooting 22 long rifle.

Yes you could get better projectiles with a 223, but moving at that slow of a speed the terminal effects aren't likely to be much better.

It could probably be done but the expense wouldn't be worth the result.

Thanks so much !

Hickok45 did a video of shooting subsonic .223, surprisingly it looked like it was still punching holes in a steel drum.

Yea, rimfire is cheaper. But if you want to build an upper shooting subsonic .223 I'd say a 16" barrel with a carbine system or a 12-14" w/pistol length system would be a good start.

Gonna need a pretty good sized gas port so I'd say an adjustable gas block, a lightweight carrier and a softer buffer spring would be good too.

I've not seen anyone actually build one from the ground up so I can't say what will absolutely work.

But I can say for sure, subsonic .300bo is WAY cheaper than subsonic .223, and there's lots of inexpensive .300bo uppers.

FWIW I have a Ruger Mini 14 in .300bo, it won't cycle subsonic unsuppressed but works fine as a 'straight pull', that is I can manually cycle the action between shots without jamming the action with a spent case. So maybe a side charger would be a better option, so if there's not enough 'oomph' to cycle, you can still do it by hand.

Just out of curiosity I'd thought about getting a box of subsonic .223 and see if it would cycle in my 10" AR pistol if I dropped in the lightweight BCG & softer spring from my .300bo pistol.
But Atomic subs are a buck a round for a 50 round box and while Detroit Ammo has theirs for half that, they never have a 30 round box in stock, smallest size available is a 120 round box.

And if subsonic .223 is your absolute goal, You may find something like a bolt action .223 is an easier solution. The Ruger American Ranch even takes AR mags.

this

Just saw this on Facebook

Attached File