I have a YHM TurboK that I originally used on a MK18'ish build (10.3" DD barrel) but I was not pleased with that setup at all. It ran fine but it was too loud and had way too much gas to the face (GTF) for my liking. I tried that same suppressor on a 16" middy and I was pleased with the performance of it on that rifle (reasonably quiet and little to no GTF). I have suppressed 300BLK SBR which covers any short/CQB type rifle need I might have but now I have no real use/need for a short 5.56/MK18 type build. That's fine but that leaves me with an unused suppressor and SBR lower that I would like to use for something? I have no specific need or purpose in mind. I just want something that will utilize those parts and that I'll enjoy shooting.

I've been kicking this around for a while now but have been frozen with indecision paralysis. I've kind of narrowed it down to 1 of 2 options...

Option #1 > 12.5" build? The thought being is it will hopefully perform better with the TurboK then my MK18 did but still be short enough to justify the SBR tax stamp and not be too long with the can installed? My concern is will it enough of an improvement over my 10.3" build? I know an adjustable gas block would solve the blowback issue but it's not going to make it any quieter.

Option #2 > 14.5" build. The thought here being that a 14.5" barrel should get me pretty close to the performance I got from the 16" gun and I already have a couple of spare 16" middy barrels that I can have cut down for the purpose (which will also keep the gas port size in check). My hang up here is using a SBR lower for a 14.5" gun seems like kind a waste of a tax stamp? That and a 14.5" barrel with a can is going to be pretty close to 20" rifle long?

I'm not running and gunning or kicking in doors so I guess the OAL isn't really an issue so I'm kind of leaning towards the 14.5" build because it's more likely to perform the way I want? The thing is, I can't shake the feeling that it's kind of a waste using a SBR lower for a 14.5" build? So one last option I've considered is...

Option #3 > Use the suppressor on a 16" AR and use the SBR lower for something else? One of my SBR lowers use to be setup for 9mm. Kind of forgot about AR9's after getting an SP5 but I still have mags and most of the parts I'd need so I wouldn't mind building it back out to a Colt 9mm SMG (635) clone?

So what sayth ARFCOM, option #1, 2 or 3 and why? Extra points awarded to those who explain their reasoning and or share personal experience with a similar setup? Super extra bonus points for posting pics of your recommended setup!

…………….

I’d do the 12.5 first. If you don’t like it, you can always sell the upper and then cut down a 16. My 11.5 is not bad at all with a .30 MG7K and A5 buffer system.

You're going to get gas in your face no matter what you decide, just to lesser degrees.

I run a 12.5" suppressed SBR and it's great.  I like the extra handguard length it affords.


14.5" SBR is silly.  I'd P&W the flash hider to keep it at 16".  Use the SBR'd lower for other fun uppers...22LR, 9mm, 300BLK, etc.

Or use a 14.5" on the SBR....it's only money.

Yeah, that might not be a bad plan?

I kind of think so too but if that's the way I go, I'm not going to bother with the P&W crap

I typically use my RECCE5 on my 10.5 and a Turbo K on my 12.5.

They are almost the exact same length. Both sound fine to my ear.

I think a 12.5 with a K can is a great setup

Thanks for the reply. What barrel did you go with? Carbine or midlength gas? Do you happen to know the gas port size? Are you running an adjustable gas block? if not, how is the GTF?

I’m using a Hodge Suppressor Optimised 12.5. I believe the gas port is .062? I don’t notice gas to the face. All my shooting is outdoors so that could be a factor.

Nice. Thanks for the reply

I love my 12.5. I have a Colt M4A1 upper cut down to 12.5". I had the gas port opened up to .068. It runs like a champ suppressed and unsuppressed. Suppressor is a KAC NT4. If you have no plans to ever shoot unsuppressed then that Hodge .062 port sounds pretty sweet but .068 seems to be my sweet spot for suppressed and unsuppressed on a 12.5. Gas to the face isn't bad but obviously there is some. That Hodge .062 port has me thinking I might try one of those BRT gas tubes and try it out as suppressed only; they have .061 and .0635 available.

For me this would be 100% suppressed and yeah, that .062 gas port sounds ideal. I really hate that so many barrel makers drill out huge gas ports to accomodate people running shit ammo. I would rather have a gas port that is too small (because that I can fix that) rather then too big and then deal with it being overgassed or need a BRT tube or Adj GB.

But assuming I won't find an affordable barrel with a .062 gas port (That hodge barrel is too beaucoup $ for me) then I guess I'll go with the BRT tube too. If those are the only 2 sizes they offer then I would get the .061 tube and try it? If that proves to be too little gas then I would use a 1/16" drill bit to open it up to .0625. I was reading a thread on another site where a guy started off with a .060 gas port and had a few issues with lock back so he opened to .0625 and said that was perfect for him.

This might be more in your price range and it is a quality mid-length gas system barrel. You could always call  them and ask about their gas port size.

https://sionicsweaponsystems.com/lawenforcement/sionics-12-5-extreme-reduced-gas-port-barrel/

Interesting. I don't know anything about "SIONICS" but I like the specs. I am curious so I will e-mail them about the gas port size.

Something else I'm unsure about when talking 12.5" barrels... Carbine vs Midlength gas system? Generally speaking I usually prefer midlength gas but when talking 12.5", I'm not sure if a midlength will have enough dwell time? Most people who have a 12.5" middy's seems to like them but I have to think there is a reason why most manufactures build carbine gas 12.5s?

Sionics makes quality stuff.

I think midlength 12.5s are usually specific to suppressor use.  Lot's of people using and liking them.

You have a registered SBR lower.  I don't understand the issue.

Build/buy a pistol upper.  Add another one later.  Add another one later again, change calibers and add another all of various lengths and set ups.  It takes a few seconds to change uppers so you can go play with whichever length/caliber suits your fancy that day.

Well I thought my original post did a pretty decent job explaining the situation but to clarify... This isn't really about "what to do with the SBR lower" as much as it is "what to do with the suppressor". It just makes sense (to me anyway) that I use one of my SBR lowers to build a dedicated upper for the suppressor.

As far as swapping out uppers, sure that's always an option but that's not really my thing. If I have a spare upper, it gets its own dedicated lower. If I have a spare lower, it gets its own dedicated upper. If I have a spare upper or lower that I don't care for enough to justify finishing it off with it's own lower/upper then I usually either just sell it or part it out and throw the parts I want to keep in the spare parts locker and sell off the rest.

Yeah, but it's not a good reason for guys who shoot suppressed. Carbine length and an oversized gas port is to ensure the gun won't choke on even underpowered bulk ammo and the lacquered steel case stuff, plus you can run them far beyond filthy. Basically they're making barrels to account for the lowest common denominator. The recoil is bad, gas to face is bad and they beat up internal parts, but they do work.

Midlength 12.5 is prime for suppressed use.  Hodge, Roscoe, Black River Tactical, and Triarc all make 12.5" middys or actually a proprietary hybrid between carbine and mid in BRTs case.

I can tell you the BRT with an H2 buffer won't cycle IMI m193 (which is not generally regarded as weak ammo), but it's like butter and 100% reliable when fired suppressed. You feel almost no recoil, close to a 22lr.

There's also a guy who will do custom gas ports and my mid 12.5 at 0.625" gas port from him is also a very nice shooter. Can't discuss the vendor here but pm if you want info.

You will notice less gas to face with a properly sized gas port. I have four 12.5" rifles btw, they're by far my favorite setup including two carbine length. Mid just lets you get away from adjustable gas blocks and stuff like that.

since you already have the lower, I vote 12.5". For gas minimization maybe an AGB?

My main training gun these days is a BCM 11.5" with AGB and Griffin RECCE5.  Basically zero gas even under sustained fire, though it gets hot as fuck.

Otherwise just slap the 14.5" on there and make it sort of a recce/dmr type gun with a magnified optic?

Thank you. That was very helpful. PM incoming

Yeah if I do the 14.5, that was the plan (recce/DMR build) but considering you don't lose much velocity with a 12.5" I'm thinking a mini recce/dmr might be fun too?

I’m doing kinda the same thing. I have a spare lower but I also have an 11” rail I like and might want to use. This makes me think I need a 12.5-14.5, but then I get analysis paralysis and end up with nothing.

I have a rattler sbr for the house and a rattler pistol for travel so I’m not sure why I’d need a pin and weld anything but here we are.

12.5". It does everything well with no tradeoffs aside from 600+ yard shots, and even then it'll make hits just not packing much oomph. Size, weight, handiness all on point, and velocity is good enough to hunt with IMO whereas I won't hunt with a 10.5" gun anymore.

Attached File

Ok, fair enough.  I just buy or build shorty uppers to plop onto my single SBR lower so I don't have to spend $200 and go through the wait for each one just to have a dedicated lower for each SBR.  I do it that way partly because all those $200 tax stamps can go toward more guns or more uppers, parts, etc.  But, that is the only lower that gets different uppers though, all the rest are single builds.  

Anyway, back to your suppressor, as for gas, one thing you can do is get a side charging upper and that will eliminate any gas coming back at you from the charging handle area.  Plus, as mentioned, the middy port and you'd get the best of both worlds.

14.5 SBRs rock. Pin and weld anything sucks.

No 11.5 OP?

At the end of the day, we all have to do what feels right for our own wants and needs. No one size/solution fits all. Luckily we all still have some options.

Nope, been there done that. It's not bad (better than a 10.3/.5) but I've come to the conclusion that if you want to go short with an AR, 300BLK is the way to go. 12.5" is as short as I'm willing to consider for a 5.56 AR.

I think I've decided to build out a 12.5" and try it for myself? If I like it great but if not then I'll go 14.5". Heck I might even just build both, shoot them side by side and decide from there?

Thank you all for the input!

@airgunner let me know if you find a decently cheap/light 12.5" barrel. I want to try this adventure too but currently saving for NV.

@steviesterno16 - will do but yeah, so far the options seem to be more limited then some other more common lengths. I'm digging that Sionics barrel posted above and it's priced nicely IMO but who knows when it will be in stock again? I emailed them Friday will some questions (including asking for an ETA on stock?) so we'll see what they come back with?

@airgunner cool, let me know what you hear back. I'm considering a different barrel length, too, just because you're right 12.5 seems tough to find.

@steviesterno16 - Will do!

How cheap? You can get a Ballistic Advantage for $90 free shipping from righttobear.com, kind of a crap shoot in terms of accuracy but they're usually decent at worst (at least my few examples over the years). Go a little over $200 and get the BA Hanson profile which comes with a pinned gas block iirc so it's pretty damn cheap all-in. They're in stock all over the place.

Slight step up is the Rosco Sage Dynamics 12.5,which has a proprietary gas length between carbine and mid. They're in stock on the Rosco site for $190. This is the barrel I'd try if I was currently in the market for a 5th 12.5" barrel lol. My one Rosco barrel is a 12.5 carbine and it's good but needs an adj gas block for suppressed.

Criterion 12.5" is available on backorder direct from Criterion in the next price tier if you're not in a hurry. They make good barrels IME and would be my 1b choice after that Rosco which I'm just curious about.

After that yeah, good luck finding Triarc and BRT barrels in stock. I put myself on some notifications and nabbed the BRT from Weapon Outfitters when it came in stock. They do pop up though, I got several notifications for both barrels within a couple months.

KAK has 12.5” mid & carbine gas value-line barrels at decent prices. The mid is over-gassed with 0.094 port but a YHM suppressor (small port) gas block is a simple way to tune with numbered drills.  

10% off sightwide with code BUILD until 9/1

https://kakindustry.com/ar-15-parts/barrels?_bc_fsnf=1&Caliber=5.56&Length=12.5%22

Get the ammo cold enough, and even IMI m193 is underpowered. I scrapped an 11.5" carbine gassed barrel after I couldn't get it to lock back after drilling the gas port to 0.125".

Cans are now out of jail, and I've got a 12.3" carbine gassed barrel on that rifle now. We shall see what kind of weather comes this winter.

Stainless 12.5, accurized mini recce. I think both Noveske and Larue offer off the shelf options. Personally I’d call WOA and have them spin up something.

For optics..

TA31w/RMR
NX8, Razor 1-6, or PA PLx 1-8
2-10 Credo or PST II

I just like spending other people’s money

I vote 12.5 with a gassed correct barrel from criterion or hodge or similar.
OR a 12.5 with a barrel of your choice, and use a BRT gas tube to get it gassed how you want without ANY adjustable GB's or etc.

I ordered the SIONICS 12.5" Extreme Reduced Gas Port Barrel. We'll see how that turns out?

Any update?
I love my 12.5" with Turbo K. I've got it setup with a BRT .0635 gas tube (.0615 gas port equivalent). Everything else is Geissele. Their upper, barrel & gas block, REBCG, Super 42 spring & H2 buffer. Haven't tried it unsuppressed yet, but it should be fine with 5.56 and a lighter buffer. I'm basing that off my 10.3" build.

It is all Geissele as well. Their upper, barrel with .063 gas port (before they hogged them out), REBCG, Super 42 spring & H3 buffer. It wears a Turbo T2. Runs unsuppressed with a carbine buffer and 5.56 ammo.

I got the barrel and put it together but I won't get a chance to shoot it until next month. Gas port on this barrel is very small (under .060) so it will be interesting to see how it runs?

I know that all too well
Efficiency of gas block and BCG come into play as well, but the Turbo K is pretty gassy. You mentioned 100% suppressed, so hopefully it works well!

The shorter the better with a can. My 12.5" suppressed feels kinda long still. Now my 8.5" suppressed feels very handy. The 10.5" isn't bad either.

Here is a pic of it (one on the left obviously) next to my Colt LE6960 (16" middy)...



Yeah funny how work and stuff can get the way of the important stuff! lol

I do plan on it being 100% suppressed but what I like about it having a really small gas port is, if I decide I want to be able to run it unsuppressed, it will be relatively easy to open up the port a little at a time till I find the sweet spot. I probably won't but it's nice knowing the option is there.

I guess it depends on your goals but for me, I've found the opposite to be true. This was a 10.3 gun and hated it so I went up to a 12.5". My 300BLK SBR was originally 9" but then I got a 7" for upper for up but after shooting it, I went back to the 9" barreled upper. I have suppressed SP5's and found I prefered the full size (8.74” barrel) over the SP5k-PDW (5.83" barrel). Longer barrels suppress better in my experience and don't find adding a couple of inches that big of a deal. my 12.5" with a K can is still slightly shorter than a 16" gun.

I ended up picking up a 14.5" barrel locally. I shot it and dialed in the gas system unsuppressed, hoping to throw the REX MG7k on it later this week. Will report back.

Update: finally go it to the range yesterday. The guys at Sionics said their barrel would not run without a suppressor and they were right. I tried that first with a couple of different loads and none of them would cycle but with the suppressor attached, it ran like a clock and would lock open after the last shot. I tried both a standard carbine buffer and "H" buffer and settled on the "H" buffer.

There is still some GTF but its significantly reduced to the point of no longer being an issue. Sound level was decent. It's not quiet by any standard but reduced enough that I was able to shoot it without earpro outdoors under a covered bench without issue. That said, it's probably worth noting that I do already have significant hearing loss so for someone with good hearing, it probably wouldn't be safe for more then a couple of shots outdoors and indoors it would probably be a bit too much?

Overall I'm digging it so far and look forward to ringing it out some more.

Sounds like a good setup!

This has me missing my old Noveske 12.5 GPR from a decade ago. The twelve-five is such a great length.

Did you ever get a measurement on the gas port size? I saw you said smaller than 0.060, but wanted to see if you knew the exact size. I have a 12.5 ERGP barrel waiting to be built up, but my smallest pin gauge was 0.073 which obviously was too small. I'll probably make this one a dedicated suppressed set up with my DA Sierra 5 since that can was crazy gassy.

I wonder what the gas port size is on the 12.5 standard gas port barrel.

Port pop is the reason ARs are louder than bolt guns to the shooter.

With my Turbo K and a 10.5 with an AGB it is just as loud as my 16" middy without a AGB.

Trick is to keep the gas escaping out of the ejection port as low as you can.

The 12.5 is a great for terminal ballistics vs length.

I cut down a 14.5" midlength gas BCM barrel to 12.5" and run a Turbo3 direct mounted. I also choke down the gas by using vented set screws in all my gasblocks and front sight bases. The vented set screws come with a .049 vent hole but this one is opened to .055. I then tune the buffer and spring for lock back. Some have H buffers and some have buffers with an aluminum weight replaced for a steel weight. They shoot smooth and have next to no gas in your face.

@waddlingweezol
The gas port on mine is .057" but it will only run suppressed. Unsuppressed it will not cycle (even with a standard 3oz buffer) which Sionics fully warns about with this barrel. If I had to guess, if you want to run suppressed and unsuppressed you would probably need to be in the low .060's range (like ~.063 maybe)?


@Joedirt199 - Do you only run suppressed? Based on my experience with mine, I can't see yours running unsupressed regardless of buffer?

Yup supressed all the time.