Suppressed AR15 in .223, 7.5" barrel, with carbine buffer?

[plodder]

For my next SBR, I am considering a .223/5.56 with 7.5" 1/7 barrel, MIL Spec carbine length buffer tube & spring and either a Specwar 5.56 silencer or one of my Form 1 silencers.

What cycling/feeding problems should I expect?

 

[Arizona_Mike]

Pistol or carbine length gas? Shoot only with silencer or with and without?

Mike

 

[plodder]

Pistol or carbine length gas? Shoot only with silencer or with and without?

Mike

Pistol length gas. Mostly shooting with silencer, reliability shooting without silencer would be secondary and not a deal breaker.

 

[Arizona_Mike]

You should not have any problems. I'd go with a standard/large gas hole (not Noveske which are designed to only cycle with a can) and adjustable gas block to allow tuning. I ran a pistol length 12" 300 BLK with a Syrac gas block 7/16 open with a can and 9/16 without a can with an H2. I ended up closing more and running the empty C buffer I usually use on semi-automatic guns with intermediate and rifle length gas.

I use a full weight M16 carrier, BTW. Often people ask about the buffer without taking into account the significant weight difference between carriers.

Mike

PS. Just to reiterate, you can do so much tuning with an adjustable gas block and save so much heartache, that the initial ~$100 is usually worth it.

 

[Ryanxia]

Arizona Mike hit the nail on the head. Larger gas hole and adjustable gas block.

I cut down a 16" barrel on one of my uppers to 7.5" (and then to 6.5") with a pistol length gas tube and never had issues. The blowback was a bit much (for reliability) but that's where your adjustable gas block comes in (which I didn't bother with at the time). You can fine tune it from there.

 

[Ryanxia]

On a side note, I took my setup with the 6.5" barrel to a vehicle tactics course and did one run with it for fun. I was in the front seat of a car with my buddy sitting next to me, when you start the drill you fire 5 shots through the windshield and exit the vehicle and continue on. You have masks and goggles on because of all the broken/powdered glass from the windshield and the muzzle blasts making you feel like you're inside a tornado.

The force of the muzzle blast was so intense it was unreal, lot of fun for me but it actually had enough power to kick up small bits of glass off the dashboard and inflict minor cuts on my buddy's nose and cheeks!
I told him next time I'm going to bring the AK SBR and sit next to him..

 

[plodder]

when you start the drill you fire 5 shots through the windshield and exit the vehicle and continue on. You have masks and goggles on because of all the broken/powdered glass from the windshield and the muzzle blasts making you feel like you're inside a tornado.

Sounds like some good, clean fun there!

 

[Ryanxia]

It's a lot of fun. Learn a lot too. Up until I took the first vehicle tactics course I didn't even think a 9mm would punch through the windshield, boy was I wrong.

The 6"/7" barreled AR's are perfectly compact, but the loss of ballistics at longer ranges seems to be quite a bit. Of course putting a suppressor on as well might help.

 

[Arizona_Mike]

Yea but 300 BLK and 7.62x39 retains about 85% of their energy with barrels as short at 10.25-10.5". Bigger bore the better with the shorties.

Mike

 

[Ryanxia]

Yes be he's talking about .223 in a 7" so it will definitely lose quite a bit of energy. My AK SBR still has plenty of energy at 10.5"

 

[Arizona_Mike]

That's precisely the reason I don't like short 5.56mm guns.

Mike

 

[wally]

Just make sure your 5.56 suppressor is rated for your ~7" barrel. Most are only rated down to about 10" barrel length -- the "uncorking" pressure is much higher as the barrel gets shorter.

 

[yugorpk]

One of the reasons I like 7.62 silencers on 5.56 guns. Pressure inside the can is lower and usually the extra volume of the bigger cans helps them being quieter too.


I run a 10.5" 5.56 SBR with a 762 specwar. Functions 100% and still gets 2500 FPS

 

[plodder]

Just make sure your 5.56 suppressor is rated for your ~7" barrel. Most are only rated down to about 10" barrel length -- the "uncorking" pressure is much higher as the barrel gets shorter.

Let me consult with the manufacturer; Oh wait, that will be me I guess I should wear the full face shield on my first mag dump (I usually do with my home rolled silencers)

 

[Arizona_Mike]

Let me consult with the manufacturer; Oh wait, that will be me I guess I should wear the full face shield on my first mag dump (I usually do with my home rolled silencers)

I've gotten accustomed to using a bandanna over my mouth and nose when shooting my side charger AR with a can. Powder burned lips are very uncomfortable.

Mike

 

[wally]

One of the reasons I like 7.62 silencers on 5.56 guns. Pressure inside the can is lower and usually the extra volume of the bigger cans helps them being quieter too.

GemTech was equivocal when I asked about using my 7.62 HVT-QD on a 7.5" 5.56. They have a good warranty (ate the tax replacing my defective Multimount 9mm) so perhaps they are being overly conservative, but I've chosen not to do it. YMMV.

 

[yugorpk]

i don't know about the Gemtechs. My Specwar 762 and SIG 762 are rated for it. Both are built like tanks.