Obviously being from NJ this is a moot point, however...

 

What's the deal with running suppressed? Why and what does it change so severely that guns won't run in both suppressed and un-supressed? As some might know (Ty, Old School) I'm not a huge AR guy but I do have one (with one more on the way) and in reading national boards the suppressor issues always pop up. It makes me curious (and jealous). This thread is simply to gain further knowledge, nothing more.

 

C

 

(I added a pic of my "Dream" AR.

 

Suppressors increase the gas pressure in the operating system.  The way a suppressor works is to delay the rapidly-expanding gasses hitting the atmosphere.  Doing so requires that the suppressor contain those gasses.  In a direct impingement AR15, this increase in pressure causes an increase in fouling but more importantly, an increase in bolt carrier velocity which can lead to malfunctions such as stovepipes and extracted cases failing to clear the ejection port.

In a direct impingement AR15, this increase in pressure causes an increase in fouling but more important, an increase in bolt carrier velocity which can lead to malfunctions such as stovepipes and extracted cases failing to clear the ejection port.

Ok. Thank you. So, what's the fix? My initial reaction would be a reduced power spring but I'm usually wrong. I guess I just don't understand the relationship between gas, gas block/tube, key, spring and buffer.

 

If it's over pressurized, what gets changed and to what and most importantly... why?

 

FWIW, if anyone ever wonders why I buy my nice stuff from Ty, it's these insights that he provides all over this forum. He is a wealth of knowledge and has never steered me wrong on a purchase.

 

C

Increase in pressure would most likely require a smaller gas port or heavier buffer... stronger spring maybe?  You wouldn't go reducing the spring power...

The fix is to slow down the carrier by either reducing the gas flow (adjustable gas block or key) or by increasing the reciprocating weight through the use of heavier buffers.  Stiffer action springs can be used however they have an additional draw back in that they really slam the action closed again.  Reducing the gas to the system will naturally reduce carrier velocity as there's less pressure acting on the bolt.  Increasing the weight of the buffer increases the amount of force needed to cycle the action which absorbs that additional energy (in the form of higher pressure gas) being shoved into the system.  

Hunh... who knew.

 

Thanks. The AR tuning stuff is very interesting to me. Not as interesting as a 1911, but it is interesting.

 

C

Tuning the gas system does apply to more than just suppressed rifles.  With a little work, you can basically eliminate muzzle rise and the majority of felt recoil.  My .308 when unsuppressed recoils slightly harder than an AR15 and has nearly zero muzzle rise.  

Does the same hold true for 300 Blk?

AR tuning its fun.  The platform is grossly over-gassed for what it needs to do in the name of "reliability", so reducing gas volume is a perfectly valid thing to do that gets you back huge benefits. You do have to understand how the platform runs, understand that it isn't really a DI system but a "internal piston sorta like DI but not really", but then it is a lot of fun to screw around with how that works. Lowering the mass and gas that make the moving bits boogie around the upper receiver can lead to really cool results.

AR tuning its fun.  The platform is grossly over-gassed for what it needs to do in the name of "reliability", so reducing gas volume is a perfectly valid thing to do that gets you back huge benefits. You do have to understand how the platform runs, understand that it isn't really a DI system but a "internal piston sorta like DI but not really", but then it is a lot of fun to screw around with how that works. Lowering the mass and gas that make the moving bits boogie around the upper receiver can lead to really cool results.

Example? Pics? I'm curious how this can all help me. I do get a bit of excessive muzzle movement with my AR. I don't have a brake (and don't really want one).

 

I have a Mega upper, MidwestPX BCG, Mcgowen 16" barrel/target crowned, standard spring and buffer in a ACE skeleton stock.

 

C

 

Ok. Thank you. So, what's the fix?

 

C

 

Buy a quality firearm.

 

I run an M16 suppressed with 3 different uppers (20", 16", 11.5") in full auto and never had a single problem and never had a single malfunction.

 

I also run an M11-nine/Max-11/M11-22 suppressed and never a problem, although I get a little gas in the face from the Max (especially without the gas block).

 

 

Buy a quality firearm.

I prefer buying quality parts and assembling myself.

 

Additionally, I'm trying to learn. It's not for everybody I understand.

Well .. it is all a system that moves from the front backwards.

 

At the front a break is the MOST important component and it makes the most difference. I understand you don't want one, but I can't not mention it because it is THAT important.

 

Moving backwards you have the volume of gas which can be controlled through the size of the gas hole in the barrel or an adjustable gas block (or adjustable gas key, when I say block assume either). Either way you reduce the amount of gas bagging around the gun. Adjustable gas blocks are a finer way to control the gas then just the gas hole size which needs to be done by the manufacturer. Plus gas ports erode over time and open up. On the other hand adjustable gas blocks break, turn off at the worst time, wear out etc. For most of the country, not a big deal, you replace it when it gets crappy, for us its a problem if we have permanent muzzle devices, so I prefer small gas holes in the barrel.

 

Next is the bolt carrier, because we don't screw with the bolt itself. Most people don't think of it this way, but the AR is not a DI platform, not really. It is actually piston driven, but the piston is bolt inside the carrier. As gasses get into the carrier, they push the bolt FORWARD (which probably needs to happen anyway to fight off barrel pressure to get the bolt lugs off the extension) and the bolt carrier backwards. This is basically an internal combustion engine where the piston stays still and the  engine block moves. This also rotates the bolt as it cams on its cam pin. Eventually the bolt is unlocked, gas rings pass the gas hole in the carrier and pressure drops, the carrier has heck of a velocity and drags the bolt with it backwards.

 

If you use a lightened carrier, the carrier needs a lot less to reach its velocity that makes everything work, which means you need less gas fed in by the gas block. Again, they work together as a system, you can lighten the carrier or you can reduce gas and you'll get something in return, you do both and you get a lot more in return.

 

And lastly you have the recoil buffer. The internet will tell you heavier is better. Sure if your gun is overgassed you want all the mass in the world to make it feel "softer", but actually it is the other way around. Reduce the gas, and everything is better, and now you can run lighter recoil buffers.

 

Also, the further you take the gas from the barrel the better, ie rifle length gas system is better then intermediate, which is better then midlength which is better then carbine. because you are running less gas pressure, less port corrosion, etc.

 

In my current race gun, I run a very effective comp, a reduce sized gas port (because damn permanent muzzled devices and I don't fully trust the key ones), a reduced mass carrier, and an EMPTY rifle buffer.  It shoots soft and flat.

 

 

 

Can this help you? I dunno. Depends what you want to do with it. A zombie Apocalypse gun should probably be over-gassed because you have no idea what crap ammo and mud you'll get in it. A 3gun rifle? Well it needs to run well with good ammo, it doesn't need to run with crap. A bench rest gun? It doesn't even need to cycle really so make whatever change you need to make it work best for you.

Thank you Vlad. Great write up.

 

C

One thing I should caution about when you go down the line of reduce mass.  The moment you reduce the mass of your carrier, you should replace the firing pin with a titanium one.  If you are running the standard recoil spring (which I am) the carrier is going to be returning with a lot more velocity (same force stored in the fully compressed spring, less mass to push forward hence more speed), but that means the firing pin will be moving forward faster. As the AR15 spring is free to move about with no drop safety or spring, that means it will have higher inertia when it slams into battery and can end up causing a slam fire. Go to a lighter titanium firing pin and you significantly reduce that risk.   

 

Also, for the same reason (velocity) make sure your mag springs are not lazy about it or the bolt carrier will overrun the feeding cycle. If your mags springs are not worn out, this is not an issue. 

I prefer buying quality parts and assembling myself.

 

Additionally, I'm trying to learn. It's not for everybody I understand.

My point was I've never had any problems and I've never seen anyone else have any problems. My 11.5" is a Frankenupper made by a gun show dude and it works great. It's the only questionable component I own, but I bought it because it was cheap and intended it specifically for burning out and turning into scrap metal, and figured I would dump it early if it was flakey.

 

Whenever I see people on the internet complain about ARs or running suppressed I figure they must have bought some sort of junk because I've never seen any of that anywhere. The thread usually contains a reference to "just as good as Colt" or "drinking the Kool Aid."

 

Personally, I would never worry about the issue of suppressing a firearm unless the barrel was too short to ensure proper early stabilization in flight or there was some other sort of know issue. I am not criticizing you for asking, I think that's a great idea. Especially since you are going to be finishing your own barrel. I'm just giving you my honest opinion based on extensive personal experience and the experience of my friends and associates. I've never seen a problem. To me, this is like reading, "How can I make my Glock reliable?" I responded accordingly. I hope you take it in the spirit it is intended.

Mipafox, thank you for the explanation. That is much more helpful to me than your initial remark.

 

Again, this is all mental masturbation for me as I live in this God forsaken state and can't own ant of it anyway.

 

C

Often my initial remark is not helpful

Relevant or or not I don't know.

 

I run a few 24" ARs..  I would think the extended length would act much like a can.

 

Most recent build has an .063" gas port at a rifle length position of course.

 

One is at .080",   It's the way I got it and runs fine.

 

But I do run M16 bolts for the extra dwell time hoping to get a little extra velocity.

Not to jack the thread, but do people running suppressed AR's still wear hearing protection or not when they shoot suppressed?

 

The bullet is still supersonic when it exits the can, is it not?

 

I know it's not like Sasha firing her suppressed AR in the Walking Dead.

I don't get to own one, but I've been around them. I would have no issues not wearing ear pro around them, however I've never been around one on a range were someone else was not shooting something unsuppressed at the same time so the point was moot.

Not to jack the thread, but do people running suppressed AR's still wear hearing protection or not when they shoot suppressed?

 

The bullet is still supersonic when it exits the can, is it not?

 

I know it's not like Sasha firing her suppressed AR in the Walking Dead.

Yes.  I still wear Surefires under electronic hearing protection.  Once you lose it, it's gone so protect your hearing as much as you can.

Few thoughts here, since I had owned and have shot suppressed. Ty is correct. always protect. sub sonic loads will allow you to not wear protection as behind the rifle is more quite then say off to one side or even farther behind. I would still wear ear pro thou with all suppressed shots. And eye pro for sure, increased blow back into the upper is crazy with dirty cheap ammo.

 

When it comes to gas port and muzzle rise and all this, loads also play a large part in this as well. My sr15e3 is one of the softest shooting AR pattern rifles I have ever shot, but if I didn't feed it 556 XM loads for the first 200 or so rounds it never would cycle. Meaning those shits had to be hot to cycle the reduced gas port that KAC uses in their barrels.  This is one of the reasons I also enjoy BCM barrels. They use a slightly smaller gas hole then most. Remember the easiest way to cycle everything under the sun, is to have a monster gas port, the negative, with decent charged loads they will have significant muzzle flip.

Not to jack the thread, but do people running suppressed AR's still wear hearing protection or not when they shoot suppressed?

 

The bullet is still supersonic when it exits the can, is it not?

 

I know it's not like Sasha firing her suppressed AR in the Walking Dead.

It really depends on many factors. What suppressor you have, what ammo you are shooting, where you are ahooting (indoor or outdoor), barrel length, etc....

It really depends on many factors. What suppressor you have, what ammo you are shooting, where you are ahooting (indoor or outdoor), barrel length, etc....

This. You'd be amazed at the difference in volume from supersonic to subsonic. And if you're using Jesse James' new suppressor than it's down to a dull whisper.... it's actually quieter than the bolt closing which, is pretty much sorcery.

Good points in this thread.

 

Just to add, with the  AR di system, its not a game of making it the softest shooting gun possible.  If you cut it too close, you run the risk of fail to eject/extract (FTE), won't chamber a round, and other bad things.  If you are adjusting a gas block, for example, a little too much is better than a little too little.

 

At the end of the day, a reliable gun is king.

 

 

Eric

Not to jack the thread, but do people running suppressed AR's still wear hearing protection or not when they shoot suppressed?

 

The bullet is still supersonic when it exits the can, is it not?

 

I know it's not like Sasha firing her suppressed AR in the Walking Dead.

The sound is greatly..suppressed...too.  You still hear the supersonic crack but the volume of noise is way less.  Think of unsuppressed as a firecracker and suppressed as a small cap gun or "popper".

 

 

Eric