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Posted: 7/27/2026 7:27:40 AM EDT
[Last Edit: Fooboy][Edited]
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Hello. I have several suppressed 16 inch rifles and strongly considering turning one into an SBR. I need to decide between a 11.5 carbine gas (probably another DD barrel) or 12.5 mid-length. If I go with 12.5 mid-length, I need a barrel commendation and a rail recommendation (11-11.5). Suppressor: Direct thread Turbo K (Gen-2, not the RB); gun will stay 100% suppressed and have an adjustable gas block (or YHM suppressor gas block) Ammo: 95% brass 55 gr m193 Optic: Aimpoint T2 Why: Given my other rifles have magnification and are 16 inches and this one has a dot, seems appropriate to shrink it so it brings more utility to the table. I do tend to like longer hand guards and considerate of back pressure (12.5 mid) but I also feel like if you're gonna SBR you might as well go short (11.5 car). If I go 11.5 Carbine: Likely go DD barrel, and 10 inch BCM MCMR If I go 12.5 mid-length: Need recommendation for barrel and 11-11.5 inch rail What would you go with and why? Note: Here is rifle in question and current condition. Attached File *** Update *** - Form 1 came back In less than one week - Retro arms cut down a new DD 14.5 mid length to 12.5 mid - I chopped my ALG EMR 13 to 11.25 - moved a Turbo K-RB to this gun (moved Turbo K v2 to another gun) Done and zeroed. No regrets Attached File Attached File |
Isaiah 1:18 - "Come now, let us reason together," says the LORD: "though your sins are like scarlet, they shall be as white as snow"
| I built my first SBR earlier this year and I went with a 12.5". I used a 14.5" Noveske mid length barrel and had it cut down. It is suppressed all the time and I went with the BRT restricted gas tube instead of an adjustable gasblock. The rail is a 11.5" Midwest Industries Combat rail. I can tell you that there are way, way 10.5" rails than there are 11.5" rails. But it still wasn't an issue to find one I liked. I also really liked the Centurion rail. It was 11 or 11.5". |
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Originally Posted By Fooboy: Hello. I have several suppressed 16 inch rifles and strongly considering turning one into an SBR. I need to decide between a 11.5 carbine gas (probably another DD barrel) or 12.5 mid-length. If I go with 12.5 mid-length, I need a barrel commendation and a rail recommendation (11-11.5). Suppressor: Direct thread Turbo K (Gen-2, not the RB); gun will stay 100% suppressed and have an adjustable gas block (or YHM suppressor gas block) Ammo: 95% brass 55 gr m193 Optic: Aimpoint T2 Why: Given my other rifles have magnification and are 16 inches and this one has a dot, seems appropriate to shrink it so it brings more utility to the table. I do tend to like longer hand guards and considerate of back pressure (12.5 mid) but I also feel like if you're gonna SBR you might as well go short (11.5 car). If I go 11.5 Carbine: Likely go DD barrel, and 10 inch BCM MCMR If I go 12.5 mid-length: Need recommendation for barrel and 11-11.5 inch rail What would you go with and why? Note: Here is rifle in question and current condition. https://www.ar15.com/media/mediaFiles/113559/IMG_9321_jpeg-3801776.JPG One thing to think about is the amount of space on the rail. Going to an 11.5” will limit the amount of junk you can put on like optic+thermal, laser, etc. All the stuff can fit, just gotta be creative. |
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Extra info since we are talking about 12.5's Attached File Hit 900 off the magazine with a 1-6 that day. That barrel is a carbine length though. |
I did a similar build a few years back, YHM TK (v1), SIONICS 12.5" "Extreme Reduced Gas Port" barrel and a MI 11.5" combat rail... The one on the left obviously I don't know if Sionics changed their ERGP barrels but when I got mine, their site was very specific about it only running with a suppressor and they weren't kidding. Mine will not cycle unsuppressed regardless of load or buffer spring. Gas port size on mine is .057 but they may have increased the port size which would then explain why they don't have that disclaimer for that barrel any more? As for barrel length... Don't even think about a 10.3/10.5 with the TK. WAY too much backpressure. I guess that could be somewhat mitigated with an AGB but I'm not a big fan of AGB's. Between 11.5 and 12.5 I think it basically comes down to what's the main goal here? The 1" difference between them isn't going to make a huge difference handling or weight wise but if OAL and/or weight is the main goal then go 11.5". If you're more concerned with performance than OAL then I'd go 12.5" which will be quieter and have better ballistics. |
On going to war over religion: "You're basically killing each other to see who's got the better imaginary friend." - Richard Jeni
| I use a turbo k on an 11.5" midlength and like it really well. Forget the barrel brand but it wasn't a fancy one. Think it was a faxon I picked up cheap at one of the AIM surplus festivities they throw a couple times a year. But it shoots well enough and is handy. It's my go-to to take with me when I travel on long road trips. |
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I just built up 2 uppers with Griffin Armament 223 Wylde 416R 5R Nitride barrels - 11.5 car & 12.5 mid. The barrels are on the slightly heftier side, which is what I want. These will be 100% suppressed, rapid fire. These should be very accurate, reliable and great supp barrels for heat / POI etc. I always use V7 hyperlight magnesium handguards and their aluminum port doors/rods, titanium BCGs etc. All rifles get SLR Titanium AGBs. All the lightweight expensive parts let me go slightly heavier on the barrel. |
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I have a 11.5” Sionics suppressor dedicated upper that I run with a YHM fat cat. It’s a well built upper and gassed nicely for a higher back pressure can, like the YHM turbo you intend to use. Purchase their complete upper and you get quite the factory package that will work well. Otherwise consider their suppressor dedicated barrels if you prefer to build to your own specs. While I can’t comment on the carbine vs mid length gas due to lack of experience, I will say a properly gassed system has more of an impact. With an Armaspec SRS H weight buffer, it’s the softest shooting of my AR’s. 
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300 yards with a cheapo psa nitride barrelAttached File I dont necessarily think its better than a 12. Its just what I got. Works fine with the yhm k rb. |
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Originally Posted By Fooboy: Where are the dang 12.5 chrome lined mid lengths in stock KAK |
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Originally Posted By Brahmzy: I just built up 2 uppers with Griffin Armament 223 Wylde 416R 5R Nitride barrels - 11.5 car & 12.5 mid. The barrels are on the slightly heftier side, which is what I want. These will be 100% suppressed, rapid fire. These should be very accurate, reliable and great supp barrels for heat / POI etc. I always use V7 hyperlight magnesium handguards and their aluminum port doors/rods, titanium BCGs etc. All rifles get SLR Titanium AGBs. All the lightweight expensive parts let me go slightly heavier on the barrel. @Brahmzy I'm planning on a Griffin Mk2 rifle and going between the 11.5 and 12.5 Wylde 416r barrel. Why did you build 2 so similar rifles- to test barrel lengths, or to serve different purpose. Can you tell me some aspects of each, which you like better and why? Thanks. |
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Originally Posted By bmarshall1: @Brahmzy I'm planning on a Griffin Mk2 rifle and going between the 11.5 and 12.5 Wylde 416r barrel. Why did you build 2 so similar rifles- to test barrel lengths, or to serve different purpose. Can you tell me some aspects of each, which you like better and why? Thanks. I’ve got a ton of rifles and am constantly changing up stuff. I fully believe in the more the merrier and I’m always chasing that “magical” build combo of various parts, configurations and suppressors. I’m also moving away from thinner barrels (never had pencil barrels, but I’ve had a lot of lighter profile 0.625 tapered barrels.) Those thinner barrels aren’t necessarily the greatest for the 100% suppressor usage that I do now (used to shoot 50/50 and now it’s pretty much suppressed 100% of the time.) So going to give solid medium profiles a try. The 12.5 GA barrel is a middy too, which I thought might be fun vs the typical carbine-length 12.5s. I’ve also never had a 12.5 before! In theory, the 223 Wylde-chambered barrels are more accurate, not to mention 416R SS and 5R rifling + nitride - those are all very good things, in addition to a slightly heavier medium profile. @Green0 Austin from Griffin seems to be a serious believer in the 12.5 length. He may have more to add. I love 10.5s/11.5s/14.5s so I figured I’d give the 12.5 a shot. The jump in weight and pointability is fairly significant between an 11.5 and a 14.5 - especially if you’re going to be hanging a suppressor off the end of the 14.5. Also, you need a pretty heavy barrel to maintain the rigidity, the longer the barrel is. I don’t think you can go wrong with either length. I traditionally really like the 11.3/11.5s. |
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@Brahmzy I can't find any evaluations or feedback on the GA HEPD barrels (Nitride SS or Chrome lined) but they look good on paper. I am at the point where I may buy a DD 14.5 middy and have it shipped to Adco or Retro arms to be cut down / threaded. |
Isaiah 1:18 - "Come now, let us reason together," says the LORD: "though your sins are like scarlet, they shall be as white as snow"
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https://www.ar15.com/forums/industry/MK2-questions/687-307729/ Good thread here ^^ |
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Originally Posted By Fooboy: I am at the point where I may buy a DD 14.5 middy and have it shipped to Adco or Retro arms to be cut down / threaded. Why? Noveske sells a 11.5 mid gas lightweight profile barrel that is excellent suppressed. No AGB...just throw a can on it, ejects nicely at 4:00, hardly any gas at all back at you...shoots flat and soft. Its the only barrel that Noveske makes that is properly gassed. |
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Originally Posted By JohnnyUtah427: Why? Noveske sells a 11.5 mid gas lightweight profile barrel that is excellent suppressed. No AGB...just throw a can on it, ejects nicely at 4:00, hardly any gas at all back at you...shoots flat and soft. Its the only barrel that Noveske makes that is properly gassed. I’ve had a ton of Noveske barrels - their 14.5 middy Afghans are very well gassed. Their 10.5s are well gassed. |
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Originally Posted By Brahmzy: https://www.ar15.com/forums/industry/MK2-questions/687-307729/ Good thread here ^^ LOL, that's my thread. I'm most likely going 12.5, but soooo many people say 11.5 I'm wondering if they found a 'secret sauce' to create the perfect rifle. I'll 99% be going 12.5 in MK2 when back in stock. But you (you're the man) got one of each! |
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The 12.5 is kind of the shortest reliable mid gas barrel. Mid gas lowers ear noise a bit vs car. The 12.5 is gassed really nice and is smooth and has 4:30 ejection. Do less of the powder burn in the can, more in the barrel, these are nice concepts. There is a lot to like about the 12.5" barrel. The 11.5 is definitely superior to the 10.5 because it is a lot more reliable- this was proven during the XM177 testing in the 60's. Then it was confirmed by the Geissele 11.5's URG getting adopted. The 10.5 does way too much powder burning in the can- it makes even the best cans sound crappier. But everything the 11.5 is doing well, the 12.5 seems to do just a little better. Our medium contour barrels are heavier than government lighter than most other heavier profiles, and they seem to hit a sweet spot between precision emphasis and keeping things lightweight. Suppressors would ideally have hosts with barrels a little more rigid than a government profile (ALA M16A2 under handguards). The suppressor adds weight, weight causes shift, also the suppressor adds pressure and heat. Medium contour to a small extent addresses all those things. |
Austin, Managing Partner - www.GriffinArmament.com
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Originally Posted By Green0: The 12.5 is kind of the shortest reliable mid gas barrel. Mid gas lowers ear noise a bit vs car. The 12.5 is gassed really nice and is smooth and has 4:30 ejection. Do less of the powder burn in the can, more in the barrel, these are nice concepts. There is a lot to like about the 12.5" barrel. The 11.5 is definitely superior to the 10.5 because it is a lot more reliable- this was proven during the XM177 testing in the 60's. Then it was confirmed by the Geissele 11.5's URG getting adopted. The 10.5 does way too much powder burning in the can- it makes even the best cans sound crappier. But everything the 11.5 is doing well, the 12.5 seems to do just a little better. Our medium contour barrels are heavier than government lighter than most other heavier profiles, and they seem to hit a sweet spot between precision emphasis and keeping things lightweight. Suppressors would ideally have hosts with barrels a little more rigid than a government profile (ALA M16A2 under handguards). The suppressor adds weight, weight causes shift, also the suppressor adds pressure and heat. Medium contour to a small extent addresses all those things. Thanks Green0, the reasoning behind your decision makes perfect sense. |
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Originally Posted By Green0: The 12.5 is kind of the shortest reliable mid gas barrel. Mid gas lowers ear noise a bit vs car. The 12.5 is gassed really nice and is smooth and has 4:30 ejection. Do less of the powder burn in the can, more in the barrel, these are nice concepts. There is a lot to like about the 12.5" barrel. The 11.5 is definitely superior to the 10.5 because it is a lot more reliable- this was proven during the XM177 testing in the 60's. Then it was confirmed by the Geissele 11.5's URG getting adopted. The 10.5 does way too much powder burning in the can- it makes even the best cans sound crappier. But everything the 11.5 is doing well, the 12.5 seems to do just a little better. Our medium contour barrels are heavier than government lighter than most other heavier profiles, and they seem to hit a sweet spot between precision emphasis and keeping things lightweight. Suppressors would ideally have hosts with barrels a little more rigid than a government profile (ALA M16A2 under handguards). The suppressor adds weight, weight causes shift, also the suppressor adds pressure and heat. Medium contour to a small extent addresses all those things. @Green0, as a manufacturer are you satisfied with 12.5" mid gas unsuppressed performance and reliability? Seems like the industry's split with makers like you, SIONICS, KAK, BRT, Triarc, and Noveske on team 12.5" mid, then DD, LWRC, Centurion, BCM, Hodge, and Geissele on team 12.5" carbine. Is team carbine just trying to ensure their 12.5s can run shit tier ammo? |
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I did a thing. Now 11.25 inches (down from 13). This will pair perfectly with a 12.5 mid. Attached File Attached File Attached File |
Isaiah 1:18 - "Come now, let us reason together," says the LORD: "though your sins are like scarlet, they shall be as white as snow"
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Originally Posted By Danus_ex: @Green0, as a manufacturer are you satisfied with 12.5" mid gas unsuppressed performance and reliability? Seems like the industry's split with makers like you, SIONICS, KAK, BRT, Triarc, and Noveske on team 12.5" mid, then DD, LWRC, Centurion, BCM, Hodge, and Geissele on team 12.5" carbine. Is team carbine just trying to ensure their 12.5s can run shit tier ammo? I only tried 12.5 mid because ian here told me about it. He suggested it works really well. He was right. Maybe the other brands don’t listen to customers? Also maybe they are in the dark ages and mostly shoot unsuppressed. If you’re running a can, the 12.5 mid is going to be unstoppable, and it’s absolutely better. If you aren’t running a can, and the gun is really dirty maybe it will hickup? I haven’t experienced that but the gun is very lean on gas with commercial ammo. What if 95% of whats different at noveske is the higher pricetag? I remember when I got suckered for 2 pacnor polygonal gain twist barrels because 12.5 was supposed to have velocity like 14.5”. That was before MSTN tested velocity and found them to be identical to regular barrels. The polygonal gain twist barrels didn’t even stabilize 62grain ammo on paper at 25yds for me so the investment was upside down and they were garbage. |
Austin, Managing Partner - www.GriffinArmament.com
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Day at the range shooting 800yds shows about 50% hit probability achieved at 800yds using a Griffin mk2 14.5 w Griffin 1-10 optic, Dual Lok 5 suppressor, and Griffin GPM lightweight cantilever mount with various 70-80 grain ammunition. At the end he rapid fires a string off a bad first call, and several rounds splash just underneath the target and he still goes 2for5rds. Would he shoot any better with a Geissele or a Noveske? I doubt it. I could see similar performance happening, but nothing wrong with this performance outside with a 10x optic and no spotter or mirage cover for the can.  ??Griffin Armament MK2 Review 800 Yard Steel Accuracy Test & Long Range Performance |
Austin, Managing Partner - www.GriffinArmament.com
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Originally Posted By Brahmzy: We really need a like button  416R barrel I assume? I just built an upper using that * 14.8 * barrel. Yeah that's the 416R nitride barrel. You can see the rifle could shoot a little better, and changing ammo is going to change POI a little bit so it's kind of like he's shooting cold bore every time he switches ammunition types. That rifle had a mil-spec trigger, not our 2 stage, so the rifle could be a little more shootable with the 2 Stage, if it had it. |
Austin, Managing Partner - www.GriffinArmament.com
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