AR 11.5" Carbine vs 12.5" Mid-Length

[Mountain_Goat_Actual]

My newest love is the 13.9" pinned a Dead Air Flash hider exactly 16.1" not too short, not too long (avoid the pistol or the SBR route)..........and with a can perfecto!

I know you asked about 11.5 or 12.5, I have had both, (though Carbine gas) flash hider, I could not tell the difference between either in sound or shooting it.................. but either is better than a 10.5". ...................both sizes are great with a can.

Faxon makes a 11.5 mid length, but recommends an adjustable gas block. Never shot one though but I see 50/50 of people loving or hating it.

My buddy has the 11.5 mid length and a sup arms bleed off block. I went with him to help him tune it and we ran into a problem while also running a surefire 3 prong muzzle device. When you back the screw out of the block to tune or lessen the gas going into the system, the actual adjustment screw ends up hitting the muzzle device shoulder like halfway thru its travel. So that limited the amount of gas we could bleed from the system, so just a heads up on that. The screw does have a deep engagement for the allen key so you might be able to shave off like a 1/8" or 1/16" of an inch to be able to back it out more to bleed off more gas OR run a entirely different gas block. However imo the sup arms bleed off block is the best block on the market so.....

Also a note, if running that setup with an RC2 can, you run into clearance issues with that same screw and trying to seat the can on the muzzle device....

I prefer a 12.5 mid length, either a triarc 2.0 barrel or the faxon 12.5 mid length gunner barrel, better dwell time AND no clearance issues. Also with the 11.5 faxon mid, it had a surprisingly large gas port....which kinda sucks to begin with, esp when running with a can.

[Skully]

Been playing with this as my newest toy;

Foxtrot Mike FM-15 11.5" Buffer-less upper.

Very unique, like an unholy offspring of a BRN180 and a normal AR. It is not Piston, still Direct impingement but side charging and buffer-less. I picked up the new generation with the 3 position Adjustable Gas block.

For the total price of $530 plus Foxtrot Mike includes the rear 1913 buffer tube adapter in the kit. A killer price given other Mfg. versions of a buffer-less upper is in the 800-1000 range.

Haven't played with it enough yet to have a verdict.

[Great-Kazoo]

Been playing with this as my newest toy;

Foxtrot Mike FM-15 11.5" Buffer-less upper.

Very unique, like an unholy offspring of a BRN180 and a normal AR. It is not Piston, still Direct impingement but side charging and buffer-less. I picked up the new generation with the 3 position Adjustable Gas block.

For the total price of $530 plus Foxtrot Mike includes the rear 1913 buffer tube adapter in the kit. A killer price given other Mfg. versions of a buffer-less upper is in the 800-1000 range.

Haven't played with it enough yet to have a verdict.

If you decide you're not liking this unit. I'll be happy to take it off your hands.

[Skully]

If you decide you're not liking this unit. I'll be happy to take it off your hands.

Dont know, really liking this one...........


If I do trade out they have a 13.9" w/ pinned Keymo mount at PA, but that version does not have an adjustable gas block, but if they do I may have to move to it and you will get first dibs Jim.

[Not_A_Llama]

My buddy has the 11.5 mid length and a sup arms bleed off block. I went with him to help him tune it and we ran into a problem while also running a surefire 3 prong muzzle device. When you back the screw out of the block to tune or lessen the gas going into the system, the actual adjustment screw ends up hitting the muzzle device shoulder like halfway thru its travel. So that limited the amount of gas we could bleed from the system, so just a heads up on that. The screw does have a deep engagement for the allen key so you might be able to shave off like a 1/8" or 1/16" of an inch to be able to back it out more to bleed off more gas OR run a entirely different gas block. However imo the sup arms bleed off block is the best block on the market so.....

Also a note, if running that setup with an RC2 can, you run into clearance issues with that same screw and trying to seat the can on the muzzle device....

I prefer a 12.5 mid length, either a triarc 2.0 barrel or the faxon 12.5 mid length gunner barrel, better dwell time AND no clearance issues. Also with the 11.5 faxon mid, it had a surprisingly large gas port....which kinda sucks to begin with, esp when running with a can.

With the Faxon 11.5 middy, it?s so overgassed that best results won?t be achieved with vent mode, and you probably won?t be able to get it to fail-to-hold-back while tuning. Do restriction mode and it?s the smoothest shooting rig available.

I?ve had a couple custom 11.5 middies cut from DD lightweight barrels, and they are able to achieve a decent tune on vent mode - you can use pliers to manually turn the screw at the end, or just chop with an angle grinder if you have brake interference.