I have a Rugged Razor in jail currently.  Its a .30 cal can.  There are no barrel length restrictions for that model and I called Rugged to confirm.

So what I would like to do is build an upper which I can run suppressed and un-suppressed if possible.  I already have a pistol lower with a 300bo upper sitting on it, waiting on the can

I had my eye on a Faxon 11.5" with a MIDLENGTH gas system here:  https://faxonfirearms.com/11-5-gunner-5-56-nato-mid-length-4150-qpq/

I'm not above going 14.5" either if that will increase performance and reliability un-suppressed as well.

I assume I would also use an adjustable gas block and be open to different buffers to get it to run reliably.

Am I on the right track here, or is there anything else I need to consider?

Gas system and barrel length are only part of the equation, as port size can have just as much, if not more of an effect, on system reliability as a whole.

The question then becomes, are those Faxon 11.5” ML barrels advertised as only working when suppressed, or only with full powered 5.56 ammo?  Any user feedback you can find in regards to that question?  Contacting Faxon may be the best step if you’re trying to get that answered.

Most commonly you’ll see Carbine length gas on 10.5”-12.5” barrels and as long as it has a properly sized gas port, you’ll be ok suppressed or unsuppressed (if not a little gassy).  Playing with buffer weights can help, or moving to an AGB or an adjustable carrier would be better.  FWIW, I’ve run numerous suppressed short barrel setups with no adjustable components in the past (primarily with barrels I had cut down and gas ports opened to my preferred specs) and they all functioned perfectly fine.

With all that said, once again depending on port size, those adjustable components may be desirable even with an 11.5” MLGS barrel, so just know going in that even small differences can add up to drastically different results when it comes to suppressed system reliability and function.

**Due to the short dwell of the barrel, the gas port will be larger than most barrels. Customers are encouraged to use an adjustable gas block for optimum functionality.

I have a MicroMOA upper 12.5" mid gas that runs great with Milspec lower. The adjustable plate hole sizes are .073/.055/.082 smallest suppressed, mid size normal, largest for very dirty gun.

I don't get it. I have an 11.5" 5.56 with carbine length gas and a Spikes ST-T2 buffer. Runs great both suppressed (Sig SRD556-QD) and unsuppressed. You don't really need to monkey with anything in order for it to run. I would imagine the midlength gas on an 11.5" barrel would cause more problems than it would solve. One of the reasons folks choose 11.5" over 10.x" is increased dwell time. Midlength gas on an 11.5" is going the opposite direction.

Hi Op- FWIW, I had a 14.5 mid-length with some messed up threads and had it cut down to 12.5. It has a fixed front sight post so no adjustable gas. I run it suppressed 100% with a standard carbine spring and heavy (I think H3) buffer. It's good to go like that. I might have thrown an adjustable bolt carrier in it before, but it has not been necessary.

I run that barrel on one of my builds. I originally ran it with a fixed gas block, JP buffer spring and a KAW valley 3.0 oz buffer. Supressed and unsupressed, it ran fine. I recently added a Superlative arms adjustable block, mainly to try and cut down on blow back and I have tuned it to were I have very little gas to the face and my brass ejects to about 2:30 while running suppressed. I have not tried it without a supprerssor since changing to the adjustable gas block.
Oh I am running a Saker 556

11.5in or 12.5in mid gas, with an SLR or Superlative AGB and a Tubb flatwire spring.

This seems like putting the cart before the horse

Normally you would pick what barrel length you want and go from there

You would consider that the most reliable setup suppressed or unsuppressed?

I have that barrel with an SLR-6 adjustable gas block, SiCo ASR brake, and use an Omega 300 suppressor. With just the brake the gas block is closed 2-3 clicks. With the suppressor it will lock back on 5-6 clicks out of something like 16.  It has a large gas port to offset the low dwell.  Biggest issue was chopping an Allen key short to get between the muzzle device and the gas block for adjustment.  It functions nicely and is accurate, about 1.5 Moa with Black Hills 55 grn and a red dot.

Are you aware Faxon uses oversized gas ports to ensure cycling with Russian garbage ammunition?  My source for this information was a Faxon rep btw. Unless I'm mistaken it seemed implied that all of their barrels were over gassed for that reason.

Wouldn't be my first pick for a suppressed AR.

Solid

With respect to using an adjustable gas block. Does an oversized port really matter in the grand scheme of things?

Thanks for the feedback y'all

I actually contacted Faxon directly.  They said to run an adjustable gas block which, while potentially unnecessary, will give you the insurance you need to make adjustments if you run into issues with your setup, or with certain types of ammo, etc.

I figured its not THAT much more to spend in the grand scheme of things and have some peace of mind as I put it together

Going with a Superlative adj block in .625 and an Aero Precision gen 2 rail, which at 1.7" internal diameter will give plenty of clearance for the gas block.  Going with a 9" because while I like the "tucked in" look, the slim profile of that barrel might flex around a bit.

The 12.5 mids can run just fine, but the 12.5 carbine runs a lot smoother even with a can, from my examples.    Based on that, my preference for 10.3-13.7" is a carbine gas system.    I think the larger gas ports needed for shorter dwell times aggravates the difference with and without a can.