I picked up a 15T (with UTG quad rail) as a dedicated host for a suppressor.
While doing some reading I noticed quite a few comments on other sites that the M&P line of ARs has a problem with too large of a barrel gas port, causing premature wear to BCG and other internal parts.
Combined with a suppressor, this makes the situation worse.

Has anyone used a suppressor on their 15 series rifle?
Is there an adjustable gas block that will fit under the quad rail?

JP - Adjustable Gas Systems

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-John

I wonder if an adjustable gas tube would be a better option (and cheaper, too).

An adjustable gas block or tube is prolly going to be your solution. You could try a heavier buffer, but this would only be a band aid until you can install one of the aformentioned.

Lance:All of the AR's I have used ( SW,Colt,RRA,DPMS,Spikes, etc) were over gassed, which will increase with a can. It is done so that all AR's work with all ammo. I do not know your experience, but as you start to change parts you may run into function problems. There are a few threads currently active on this forum, check out JaPes's threads/post and you will find some excellent info related to your question along with suggestions of gear and ways to approach a problem. Be Safe,

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I BACK OUR BLUE

I have also heard that they are over gassed to work with all ammo, but I really wonder if that is correct. Could it be that they are using the same size gas port as the M4, yet the pressures are different due to the additional barrel length on an AR-15? Are the rifles with the 14" barrel and welded on flash hiders to equal 16" also over gassed? I just can't see that in the day of mil spec this and that, that vendors would all use different size gas ports.

This rifle will only be used with a suppressor and at some point, with only one type of ammo. (Dedicated coyote rifle.) So, it would be best to get it sorted out once and for all.
I considered a heavier buffer/spring combo which will alleviate the battering of parts, but doesn't solve the excess gas issue I face (literally).
I recorded all the dimensions of the gas block and no one seems to make one that will fit within the confines of the factory handguards, without slightly modifying the block or handguards.
Syrac comes closest, so I may give them a call and get some advice.

I was hoping someone had already faced this issue and I could just piggyback off their research, testing and hard work!!

AMEN!!!!! Although it's more that if anyone wants to sell barrels, they're going to use mil-spec designs & tolerances to increase the potential market. It also saves bags of money not having to re-engineer the gas system.

BTW, barrel length after the gas port has minimal effect upon the gas system pressure. FWIW, gas system dynamics are considered fluid dynamics. The general principles aren't really complex but figuring out specific features to achieve a desired result can be.

Just about every carbine is over gassed, if you go down the road with an adjustable block or tube your going to have to end up setting up for one specific load to ensure reliable cycling. However with your comment that you are indeed planning on staying with one load that should not be a problem.

I have a different AR than yours, but I have had to deal with suppressor/over gassing issues. I’m not an AR expert by any means but I have built a few from the ground up so I might be able to help or at least pass on my successes and failures.

Background: Seekins billet upper/lower, 16” Rainier Arms Ultra Match 223 Wylde, SP3R V3 12” hand guard, mid-length gas system, JP Enterprises Adj lower profile gas block, yadda, yadda, yadda.

As far as I’m aware, the gas hole in a mil-spec barrel is the same from one to another. They are generally ‘over gassed’ to cycle not only different kinds of ammo, but also to overcome dirt/debris from combat use. The extra gas allows the carrier to push through the carbon, sand, dirt, etc… as well as more reliably fire a variety of ammo.

Once you add a suppressor, it causes resistance in the amount of gas that’s normally allowed to escape with the round and it takes the path of least resistance (i.e. back to you via the block, gas tube, carrier, and in many cases through the charging handle into you face.

Arguably, the extra gas might cause premature wear of your parts, but there again, there are many ARs that have literally tens of thousands of rounds fired suppressed w/o an adj GB.

With that said, I decided to install an adj GB. I’ve had pretty good luck with JPs version. It allows adj via a screw. The more you tighten it, the less gas, and the other way around for more gas. At one point I was able to find a balance where I was able to get reliable function with the same gas setting suppressed and unsuppressed using LC 162 gr green tip. If you regularly switch ammo, YMMV.

Generally if you dial the gas setting down to fire suppressed to avoid ‘gas face’, if/when you take the suppressor off, there won’t be enough gas to cycle the next round. It basically short strokes, ejecting the brass but it won’t go far enough back to load a new round.

When I found my goldilocks setting, I marked it with a sharpie and used some Rocksett to keep the adj screw from backing out. You don’t want to use locktite or similar stuff in this application because it won’t take the heat that a GB will generate. Rocksett will.

All was good for @10K rds of flawless function but the last time I was out, I found the setting had changed…I’m assuming from the recoil…and it essentially became a single shot. I’d fire, the bolt wouldn’t move, I’d pull the charging handle back ejecting the spent casing and loading a new one, fire, repeat….sucked!!!

To get through the rest of the day, I backed the screw out ensuring reliable function, but pretty much went back to over gassing the gun. It definitely changed the recoil impulse and wasn’t as smooth, but it worked. I haven’t had the range time to find that balance since.

Backing up a bit, the reason I bought the JP version is that I ran into similar clearance issues that you’re concerned about with my hand guard. I would have loved to have gotten a Noveske switch block (lever adj), but the profile was too high and it comes preinstalled on the barrel. Even if it would have fit the next issue is that the GB is under your hand guard so unless there’s a cut out in your hand guard you can’t access the lever. As it is on the JP version, I have to access it from the side between the vent holes with a fairly long allen key. I keep it stored in my stock JIC.

I’ve heard good things about the Syrac system. At least it allows the ability to lock your setting down without the use of ‘glue’. I have yet to try one though so I can’t speak from personal experience. Profile-wise it should fit under most hand guards. You may run into the same access issue(s) if you ever want to switch gas settings based on ammo, because you have to access it from the front or squeeze an L-shaped allen key between your hand guard vents from the side.

Ideally, you’d want something with a lever or dial with multiple settings. Downside is that I’m not aware of one that will fit under a low profile hand guard unless you dremel an access channel into your guard. Even with that your optic, BUIS or something else might be in the way for top access.

Of course the other option is to get a shorter hand guard that exposes your GB. I’m not willing to do that yet.

Hope this helps.

You got me looking now and in the fews years it's been since I've last looked there are already other options that look promising.

Here's one that looks interesting:
Govnah Gas Blocks | MicroMOA

Besides being low profile, since it doesn't require a screw adjustment the fouling that normally makes adj difficult are no longer an issue since you push a plate adaptor.

Mfgs have a major goal of minimizing customer complaints , both for direct warrenty expenses , and bad word of mouth ( word of internet ). This inducess them to err on the side of maintaining function with any ammunition , under conditions of abundance of crud and minimal lubrication.

16in bbls with carbine gas systems are more enherently prone to over gassing than 14.3 inch w/ carbine gas system , or 20in with rifle gas.

Supressors inherently keep the gas pressure higher , for a longer time.

So that will be a tripple strike against you.

From what I understand from my gunsmith friends who regularily deal with AR's and supressors - starting from known overgassed condition , keep experementing with extra power buffer springs , progressively heavier buffers until ejection pattern is within acceptable range. Then also test for function unsupressed. Usually , but not always a compromise setup will allow for all ammo function both supressed and unsupressed. But sometime one of the modes will require specific ammo.

If you want to fix the problem then get the Innovative Arms W.A.R. receiver. This provides a user selectable gas valve right on the upper receiver.

http://innovativearms.com/

It makes a big difference.

Just installed the SLR Sentry 7 gas block on my 15T. Fits fine and very happy with results. Rifle felt over gassed from the beginning and WAY over gassed with suppressor on. Definitely recommend if you are going to run suppressed.

I'm a little late in replying to the OP but here is a good gauge to tell how your rifle is doing and how much gas it is getting.

Ejection from 12:00 - 3:00 = Over Gassed

Ejection from 3:00 - 4:30 = Perfect

Ejection from 4:30 - 6:00 = Short stroking

I've got a Syrac. It's different than some others in that the adjustment is on a quarter turn detent rather than having to fiddle with a locking screw. Just adjust it where you want and leave it. I don't shoot mine suppressed but it made a significant difference in softer shooting and less muzzle rise.

Wouldn't a gas piston upper negate all these problems?

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S&W Accumulator

The main problem with piston guns is that they are louder than gas guns when suppressed.

Another option is a heavy or extra heavy buffer.

VLTOR A5 buffer system, and a few of the heavier buffers to experiment with. You might cure what ails you with this alone -- it's an incredible system.

After that, if needed, add an adjustable gas block.