View Full Version : question on AR suppressor

Bawana jim
March 14, 2015, 11:35
Have a Gemtech entry suppressor and put about 60 rounds through it on my AR. I noticed my brass coming out really dirty so looked into the mag and saw a lot of carbon getting blown back into the chamber and down into the magazine. Gun was getting dirty real fast. Is this common with a suppressor on?

Took gun apart to clean it and a lot of carbon on the tip of the barrel. Had to scrape it off so wondering how much before it's going to affect accuracy.

March 14, 2015, 12:13
Gun was getting dirty real fast. Is this common with a suppressor on?


Common and no way to stop it.... except for taking off the suppressor.

March 15, 2015, 09:36
Totally normal. .22's are even worse!

March 15, 2015, 09:46
Totally normal. .22's are even worse!

+ 1

March 15, 2015, 12:15
It's the back pressure from the can holding the gases in - you can use a 30 cal suppressor on the rifle and it doesn't force as much stuff back into an AR and if you have a piston AR it won't dump as much stuff into the action. But yeah your experience is normal - Oh and don't forget to put Never sez on your threads unless you want permanent attachment then use locker like rockset.

March 16, 2015, 10:34
It could be fixed with a custom gas block or an adjustable gas tube.

Both are available.

March 16, 2015, 15:20
It could be fixed with a custom gas block or an adjustable gas tube.

Both are available.

I don't know if FIXED is the right word. Maybe IMPROVED would be a better descriptor?

March 16, 2015, 15:52
You could certainly dial the gas back at that point to have the same amount of gunk blown back into the receiver as when the can is not there.

But adjusting back and forth would be a pain.

March 16, 2015, 17:03
I've got one of these on order to try:


It's two position, but you can get different plates, or one that is only dimpled to drill yourself as well as three position. Thought a three position Normal/Off/Suppressed might work well.



March 16, 2015, 19:53
Very nice, thanks Shortround!

More complicated that what's in my head, but fast to actuate and you could easily tinker with orifice size.

March 16, 2015, 23:56
Very interesting - thanks for posting

March 17, 2015, 00:30
Been thinking about variations on AR can/adjustable gas blocks/gas and carbon blown back into the action.

Except for the price (I can buy/build 2 AR for the price of 1 FAL) it's all bandaids on the original Stoner design. Which is genius. Remember the design of gas operated guns went from the M1 to the M16 in what, 25 years? There's no easy way to get the same range of gas adjustment that's on every FAL on an AR. Plus the FAL is going to need cleaning about 1/100 as much as an AR. Hell, I left mine dirty for 4 years, no ill effect. Shoot only non corrosive ammo and make sure it's not got any water on it, and it just works.

I'm building 2 AR 300 Blackout just for kicks. So I'm learning a lot about that action. It's light, genius, and I'm amazed it works at all let alone as reliably as it does. The downside is that, apparently, you basically have to hose it down with lube every now and then right in the middle of major range time or in competition. Excuse me? Aren't battle rifles supposed to go bang until you run out of ammo? Which might happen after you overheat the barrel? What's the point of heat resistant handguards if the action locks up with carbon fouling before they get that hot?

I'll keep the ARs I build because they are a fun project and one's for my daughter. But the "going bang until I run out of ammo" gun is my FrankenFAL.

March 17, 2015, 21:16
You could make piston-driven ARs...that DOES solve the 'pooping-where-it-eats' problem.

Honestly I feel the piston, bolt(+carrier), and recoil spring setup on the FAL is WAAAY bigger than it needs to be.

I want to make a FAL with bull bbl, custom gas block to keep bbl thickness, adjustable gas system, hard-mounted between receiver and gas block, dissipator length block separation from receiver, and then partial gas piston from about halfway back.

But I have too many hobbies and a 9yo, sooooo...

March 24, 2015, 19:46
First, an adjustable gas block will help in a 5.56 suppressed AR. But you will still get a considerable amount of garbage into the action. In no way will it be the same amount as unsuppressed. And while a piston system runs cleaner under normal conditions it doesn't really help much when running a suppressor. The garbage that gets into the action in a suppressed rifle comes from the barrel not the gas system. If we are talking 300 BLK you want to run a pistol gas system and you don't need an adjustable gas block.

March 24, 2015, 21:25
In all cases reducing the gas to the actuation mechanism will help reduce the fouling.

All we are really doing is taking advantage of the overgassed and delayed gas system and retarding the system to try to minimize blowback when the case is extracted.