subsonic, can it be done?

[Lloyd Smale]

Ive got a 223 supressor in the works for my ar15s. Is there anyone that sucessfully loaded subsonic in an ar that would still run an action and feed out of a mag? Jacketed or cast?

[KYShooter73]

I did find this: http://hodgdon.com/PDF/Trail%20Boss%20Reduced%20Loads%20R&P.pdf

No idea if it would cycle the action. A few brands of commercial subsonic .223 out there. I would worry about baffle strikes trying to load a overly heavy round in a .223. I have a .223 can. Makes about as much noise as an unsuppressed .22lr. If I just had to go subsonic with my ar, And have it cycle, I would go with a .22 conversion kit.

[Larry Gibson]

Odds of that are slim to none with slim being gone.

Worked at that for some time with both cast and jacketed. All I succeded in was no function or bullet stuck in barrel just past the gas port. What little psi there was to push the jacketed bullet at subsonic levels was vented away at the gas port and the friction stopped the bullet in the barrel. With BE and Unique I don't recommend loading below 1200 fps as a stuck bullet can easily occur. Lots of subsonic cast loads w/o sticking the bullet (less friction with cast) but w/o functioning.

If you want subsonic with funtioning out of your AR then one of the .22LR bolt replacements is the way to go. I've a M261 and it works wonderfull in my 12" twist AR.

Larry Gibson

[Artful]

I have never seen a reliable AR with subsonic - I have seen one that functioned sometimes (usually just first couple when clean). Mr Gibson's advise is sound - or just buy a fast twist barreled 10/22 that's suppressed.

[warboar_21]

You would really need an adjustable gas block to do what you are wanting. With the port closed you will have enough pressure to make it out of the barrel and the residual pressure from the baffles should cycle the bolt. You may need to change the spring and a lighter weight buffer to aid in cycling.

You could learn more about this from AR15.com as there are many people on that site who run suppressors and sub sonic loads in several different calibers.

I do believe JP Enterprise carries the adjustable blocks as well as a few other manufacturers.

[Lloyd Smale]

Ive got a smith ar22 to use it with 22lrs. I didnt hold much hope for getting one to run. Most of the heavier 70 grain plus bullets dont run semi auto to begin with. Oh well

[cpileri]

CorBon was supposed to come out w a 100gr cycling 223, but it did not meet their expectations. Some savvy reloader might start there and develop a heavy cast load that might work. Just an idea, not surehow to proceed myself. Maybe its a start, though.
C-

[bikerbeans]

FWIW, only the heavy, 208g and larger, 30 cal projectiles are recommended for subsonic loads in an AR platform 300 AAC. To me this seems that getting a subsonic load with a 55 to 70 grain projectile that will cycle your AR would be a real stretch.

Kinda off topic, but I have heard many say use an adjustable gas block. An adjustable gas block would allow you to reduce the pressure felt on the bolt but I don't see how this would help the cycling of a subsonic weapon. Maybe a larger diameter gas port with a bigger ID gas tube would help, assuming that is a modification that is possible.


BB

[garym1a2]

If you do get an AR to run subsonic even with 77 gr bullets you have less power than a 380acp.

[Lloyd Smale]

thats a good point too gary.

[Baron von Trollwhack]

FWIW, 6.3 of green dot/55 gr. Varmint extreme runs @ 2100fps in my bolt gun with excellent accuracy. Did not try in AR though. This may be a starting point. If I was trying your project I would start with the buffer spring strength reduction.

BvT

[popper]

adjustable gas block & open the bbl gas hole.

[bikerbeans]

I just run a couple of subsonic .224 bullets through a stability calculator using a 1:9 twist and the magic 8 ball said they aren't stable.

bb

http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

[bigfelipe]

It just won't go that slow AND build the pressure to cycle the bolt AND be stable. That's why 300blk exists. If you want to shoot subs, build a BLK or go single shot.

[roadrunner0]

They suppress the 9mm variant of the M4 platform or is it the XM177.. Very short distance between the gas port and barrel crown with a long flash suppressor tube.. At least it is shorter then the AR and the op spring is different some have a kick piston.. The .556 is suppressed somewhat but just not that well and the round is not that effective.. You use to see a lot of MP5's set up in 9mm with suppressors carried by British special forces/black ops so it must have worked as a good quiet bullet hose..

[armedmoose]

Consider a barrel change on your AR15 and go .30 caliber on your suppressor...

http://castboolits.gunloads.com/showthread.php?202824-300-Black-Out-what-is-this

[2wheelDuke]

I agree with the others on not re-inventing the wheel. A .300blk upper and .30 suppressor would beat a subsonic .223.