AR-15 Possibly Overgassed

[Ted S.]

Went to the range to shoot and zero my new optic. In short, I noticed a few odd things. Not about the optic though, it works great.

1. The brass casings were ejecting at about 1:00-1:30. I noticed this after seeing most casing land in front of the shooting bench at the range. Last time I was at the range, I really did not notice, but I was firing so steel cased WOLF and Tula ammo.

2. The gun had a lot of kick for 5.56 ammo. Last time I was at the range was in September, and as noted above, I was using steel cased Russian ammo. So I either did not notice then, or expected it from the ammo.

3. The gun ran very dirty. Before I think I blamed the Russian ammo. :tinfoil:

4. I really only noticed this today, but the casing that fell into my range bag had similar wear markings in the same general areas of the brass.

I remembered having read a few things on this forum about overgassing issues in some ARs, most notably one by Dolomite. So, after some correspondence with Dolomite, I opted to order an adjustable gas block to see if this may resolve the issue.

I would like to point out that I am assuming this problem is an overgassing problem. My AR is has a carbine length gas tube. I also recall that from one of my earlier modifications to the rifle, I had a full length buffer because I changed the stock out to a Magpul PRS. After that swap, there was a very noticeable reduction in felt recoil. I've recently, within the last quarter of the year or so, I've converted the gun back to a collapsible stock, albeit a different one than before, but using the same old lighter buffer. I can only assume further at this point the following:

1. The heavier buffer compensated or band-aided the real issue of over gassing.

2. This rifle may have always been overgassed. I just may not have noticed at first because I was a major newb to ARs before and after putting the PRS on my rifle.

3. I have an irrational and implicit bias that Russian ammo is junk.

A few notes on the variables that i can recall from the range:

1. Shooting was conducted between 25-50 yds. Probably completely irrelevant.

2. Temp was in the 70s while at the range.

3. There was some wind. Not enough to affect shooting at those distances, or affect where the brass went after ejecting. (I was shooting almost against the wind, the wind was blowing in my direction from about 11:00.

Some pictures of the brass after the fact:

 

[URL=http://s1160.photobucket.com/user/Ted_Stevens/media/71bd6835-c1a3-4c5a-a226-577f5d2bd2ff_zpsa9e0be10.jpg.html][/URL]

 

[URL=http://s1160.photobucket.com/user/Ted_Stevens/media/dc428124-8eee-4830-a332-3a89029ade96_zpse33e7e3c.jpg.html][/URL]

[Ted S.]

Forgot to mention, I'm going to take Dolomite's advice and swap out the gas block with an adjustable gas block and attempt to correct the issue. Will report once this has been tested.

[Oh Shoot]

Assuming everything else is up to snuff, earlier than 3:00 ejection pattern does indeed suggest significant overgassing.  Dunno exactly regarding the casing dimples though.

 

So, confused about the adjustable gas block, are you using one or not?

 

edit: okay, see you answered that while I was typing.

 

- OS

Edited December 23, 2013 by Oh Shoot

[Ted S.]

Assuming everything else is up to snuff, earlier than 3:00 ejection pattern does indeed suggest significant overgassing.  Dunno exactly regarding the casing dimples though.

 

So, confused about the adjustable gas block, are you using one or not?

 

edit: okay, see you answered that while I was typing.

 

- OS

 

Sorry about that, put so much thought into writing the first post that I forgot to mention about the gas block, that's why I went ahead and replied. I didn't want to confuse anyone who may already be reading it too much.

 

The one currently on there is the standard A1 style gas block/iron sight. Sorry about the confusion once again.

 

EDIT: Should have corrected this sooner, the rifle has an A2 style front sight...

Edited December 24, 2013 by Ted S.

[Oh Shoot]

Sorry about that, put so much thought into writing the first post that I forgot to mention about the gas block, that's why I went ahead and replied. I didn't want to confuse anyone who may already be reading it too much.

 

The one currently on there is the standard A1 style gas block/iron sight. Sorry about the confusion once again.

 

A heavy H3 carbine buffer might compensate enough to tame it down into spec, but yeah, an adjustable block undoubtedly offers the most control.

 

And sure, a combination of rifle buffer and Russian ammo may have run just about right before on your rifle. Rifle buffer is a bit heavier than even H2 carbine buffer. I shoot a lot of Russian steel, and find it quite satisfactory, but none that I tested has ever hit 3000 fps, so it's underpowered compared to military spec 5.56 or hotter commercial .223.

 

- OS

[Ted S.]

I usually just shoot 55gr 5.56 or .223 because of availability, but I'd like to go as heavy as I can as soon as I cycle through my lighter ammo. Hope calibrating fo the gas cycling on the lighter brass cased rounds doesn't mess that up....but I'll have an adjustable gas block at that point, so I guess I can always readjust at that point...all assuming the problem is overgassing in the first place.

[scoutfsu]

What kind of rifle/upper is this?

 

5.56 ammo or .223 ( I suspect .223 based on the Russkie comment).  If your rifle is overgassed on Russian ammo, either the gas block or gas tube needs to be replaced.

 

The buffer tube (RE) doesn't matter one bit.  Yes, it can change the feel of how the rifle shoots due to a heavier buffer...but that doesn't mean the rifle isn't still overgassed.

 

Temperature and wind have zero effect on it.

[Ted S.]

What kind of rifle/upper is this?

 

5.56 ammo or .223 ( I suspect .223 based on the Russkie comment).  If your rifle is overgassed on Russian ammo, either the gas block or gas tube needs to be replaced.

 

The buffer tube (RE) doesn't matter one bit.  Yes, it can change the feel of how the rifle shoots due to a heavier buffer...but that doesn't mean the rifle isn't still overgassed.

 

Temperature and wind have zero effect on it.

 

The barrel is chambered 5.56. It can shoot .223 as well. As noted earlier, my first troubleshooting of this problem will be switching to an adjustable gas block to suppress the gas that cycles back.

 

Hopefully I can make it to the range the weekend after the gas block swap to report if this is a resolution.

Edited December 23, 2013 by Ted S.

[scoutfsu]

The barrel doesn't matter.

 

You're most likely looking at an oversized gas port.  What kind of rifle/upper is this? 

 

An adjustable gas block is a solution but not THE solution if that makes sense. You can slow things down by playing with buffer weights, springs, BCG's.....but overall, an oversized port is the root cause.  Adjustable gas blocks should be your last resort (unless you're specifically using it for a suppressor or tuning it for games like 3 gun).

[Ted S.]

Stag arms, Model 1.

 

http://www.stagarms.com/model-1/

Product Specs

Action: Semi-auto direct impingement

Chamber: 5.56 NATO. This rifle will also shoot .223

Twist Rate: 1/9 button rifled

Muzzle Device: A2 flash hider (Stag Arms Compensator on post ban models)

Barrel: 16", 4140 steel, chrome lined, government profile, manganese phosphate coated

Handguard: Thermoplastic with double heat shields

Upper Receiver: Forged and mil-spec 7075 T6 aluminum with type 3 hard coat anodizing and a picatinny rail on top

Bolt Carrier: Enhanced semi-auto with a manganese phosphate coating

Charging Handle: Standard mil-spec

Front Sight: F-marked A2 front sight, side sling swivel, and bayonet lug (no bayonet lug on post ban models)

Rear Sight: Removable A3 carry handle with integrated sight

Lower Receiver Material: 7075 T6 aluminum with a type 3 hard coat anodizing

Hammer/Trigger pin size: Mil-spec small pin .154"

Pivot/Takedown Pin Size: Mil-spec small pin - .250"

Caliber Marking: 5.56 NATO

Buttstock: Mil-spec 6 position (Post-ban stock looks the same non-adjustable at the furthest extension)

Buffer: Standard carbine buffer and spring

Trigger: Mil-spec single stage trigger with a non-adjustable 5-8 pound trigger pull

Grip: A2 style plastic grip

Magazine: 30rd (Post-ban versions will have a 10rd magazine)

Safety Selector: Right Hand

[scoutfsu]

Without mic'ing your port, my money is on that, an oversized port....for what little its worth.

 

Again, an adjustable block can be a good thing if you understand what its for and why you're using it.  IMO, it is to tune weapons for suppressors or rifle games like 3 gun.  Nothing wrong with that.....but I don't think it's the solution for a simple overgassed port.

[Ted S.]

Without mic'ing your port, my money is on that, an oversized port....for what little its worth.

 

Again, an adjustable block can be a good thing if you understand what its for and why you're using it.  IMO, it is to tune weapons for suppressors or rifle games like 3 gun.  Nothing wrong with that.....but I don't think it's the solution for a simple overgassed port.

 

I'm going for the adjustable gas block because it should fix this issue, and it allows for oppurtunity in the future. Kind of like what you have mentioned about the suppressor. I may have a suppressor for this gun one day, who knows? I don't see a need for one at the moment, but that may change in the future.

[Oh Shoot]

.....but I don't think it's the solution for a simple overgassed port.

 

Half the ARs out there come with with biggest port possible within the (debatable) specs and are overgassed to some extent, as the manufacturers want to make sure they run period.

 

What, though,  is your solution for an oversized port, though, if not heavier buffer/spring, or often best, adjustable gas block? Weld it up smaller? What's the difference, you're making the aperture smaller before the gas tube either way. Buy a new barrel?

 

When you get one that is so overgassed that it's throwing empties out at 1:00 and overrides the mag to where it doesn't even pick up the next round, and you put an adjustable block on it so that it slings them at 4:00 and runs 100%, I'd call the thing fixed, myself.

 

- OS

Edited December 23, 2013 by Oh Shoot

[Luke E.]

Half the ARs out there come with with biggest port possible within the (debatable) specs and are overgassed to some extent, as the manufacturers want to make sure they run period.

 

What, though,  is your solution for an oversized port, though, if not heavier buffer/spring, or often best, adjustable gas block? Weld it up smaller? What's the difference, you're making the aperture smaller before the gas tube either way. Buy a new barrel?

 

When you get one that is so overgassed that it's throwing empties out at 1:00 and overrides the mag to where it doesn't even pick up the next round, and you put an adjustable block on it so that it slings them at 4:00 and runs 100%, I'd call the thing fixed, myself.

 

- OS

 

 You beat me to it OS but I was going to ask the same question. I sure can't see tossing barrels in the scrap bin until I get one with a gas port that is "just right". And just right for what? I may change ammo and all the sudden it is no longer "just right". I think being able to tune your gas system is a valuable thing regardless of whether or not you're going to be shooting 3gun. Ted S. unless something new is brought to my attention i'm going to say stick with the adjustable block idea as Dolomite has i'm sure explained well to you and OhShoot mentioned above. IMO having a great trigger, a nice sight/optic and a properly tuned gas system make for a really good rifle.

[Dolomite_supafly]

Adding a heavy buffer and heavier springs only slows the bolt carrier down. The bolt is still unlocking earlier than if you have the gas adjusted to a proper level. And when it unlocks earlier the pressures are higher in the barrel and that blows more crude into the receiver and possibly into the shooters face. The gun unlocking early also causes more wear on the locking lugs. Adding a suppressor over gasses a gun too so why not do the same if a gun is over gassed without a suppressor. You do not hear of people adding heavy buffers when they run a suppressor, what they do is they reduce the gas.

 

There is a set pressure range at the carrier. I forget but rifle is somewhere under 19K psi and carbine is something like 34K. Now you can take an adjustable gas block and artificially lengthen the gas system and reduce pressures. You can take a 34K carbine gas system and adjust it down to the 19K rifle port and reduce the amount of crude, felt recoil and wear. From the gas port back all AR's are the same so you can reduce the high PSI of the carbine length gas system down to the PSI of the rifle system without issue.

 

The root cause of an over gassed gun is too much gas pressure reaching the bolt carrier. This causes the bolt to unlock earlier when the pressures in the barrel are still higher compared to a properly gassed gun. The easiest cure for reducing the pressure that reaches the bolt carrier is through the use of an adjustable gas block. A heavy buffer does nothing to reduce the amount of pressure reaching the bolt carrier.

 

Adding a heavy buffer adds unnecessary weight to the gun. And when that heavier buffer bottoms out on the buffer tube it causes more felt recoil that if a lighter buffer were used with an adjustable gas block. An upper should be what is tuned, not the lower. The reason why is the lower is supposed to work with any upper. If you monkey around with the lower because of a over gassed upper then when you put a properly gassed upper on that lower you are going to have cycling issues.

 

Another big reason to run an adjustable gas block is that over time the gas port itself becomes enlarged and elongated. This, in turn, increases pressures as well.

 

I have said it before, the heavy buffers were made by manufacturers to deal with their over gassed guns. And the reason why they make over gassed guns is likely for two reasons. First is so the gun will cycle with crappy ammo. Second is because they use the port size for a real M4 with a 14.5" barrel on their 16" M4 clones they make.

 

BTW, I have used a chronograph to test a lot of combloc ammo. I have yet to find a 55 grain load that has a velocity above 2,900 fps out of a 16" barrel.

[scoutfsu]

If it were my barrel, I'd either have Marvin Pitts or ADCO weld it and drill a new port.  That depends on who makes the barrel, if it's even worth it.  You guys are correct.  The easiest thing to do is put on a good adjustable gas block and call it fixed.  Absolutely nothing wrong with that course of action.

[Ted S.]

Ended up ordering this gas block: http://www.jprifles.com/buy.php?item=JPGS-1

 

Broke the gas assembly down and am currently waiting for the new gas block. I will report the results as to whether the issue is remedied or not as soon as I can get to the range with the new gas block (hopefully the weekend after installing).

 

[URL=http://s1160.photobucket.com/user/Ted_Stevens/media/DSC01284_zps55b842fb.jpg.html][/URL]

[Luke E.]

Ended up ordering this gas block: http://www.jprifles.com/buy.php?item=JPGS-1

 

Broke the gas assembly down and am currently waiting for the new gas block. I will report the results as to whether the issue is remedied or not as soon as I can get to the range with the new gas block (hopefully the weekend after installing).

 

 

 That gas block is going towork great but you WILL have to use blue loctite on the adjustment screw because unless they have changed something the screw has a bit much play in it. This won't be a problem because once you settle on an adjustment you add the loctite and all is well. I think you will like having the adjustable block.

[Monkeyman2500]

Anyone know the lowest profile adjustable gas block. Have to fit one under a jp/vtac handguard.

[Luke E.]

Anyone know the lowest profile adjustable gas block. Have to fit one under a jp/vtac handguard.

 

 

 Check out the Syrac. That's what I am going to use on the rifle i'm building now. I read A LOT of reviews (on Midway and a few other popular sites) on different adjustable blocks that claim to be very low profile and there were many reviews stating that they were pissed because their handguard wouldn't fit and that they should have just spent the money on a Syrac to start with. I'm guessing I saw 20-30 reviews that were very similar to that. I can't say for sure that there is nothing smaller but it sure seemed to me that there was a lot pointing towards them being smaller than most of the usual suspects. There adjustment system is also top notch IMO

[Dolomite_supafly]

I have one of these and it is great.

http://www.ebay.com/itm/BLACK-Stainless-Micro-Adjustable-Gas-Block-750-Mil-Spec-556-Made-in-USA-By-BTE-/171199312132?pt=LH_DefaultDomain_0&hash=item27dc463104

 

http://www.ebay.com/itm/Stainless-Micro-Adjustable-Gas-Block-750-Mil-Spec-556-Made-in-USA-By-BTE-/181243919159?pt=LH_DefaultDomain_0&hash=item2a32fabb37

[Ted S.]

New JP adjustable gas block is on. Going to test it as soon as I get to the range. I'm on call tomorrow and probably next week too, but I will try to sneak over there for a bit one day.....

[Ted S.]

Looks like I will also have to replace the front iron sight with something that compensates for the lower setting gas block rail. Not too worried about that until I know the problem is fixed.

Edited December 29, 2013 by Ted S.

[Ted S.]

Finally made it to the range to test this gas block out. Works as needed, and corrected the overgassing problem. Brass ejects at 3:00 to 4:30 depending on how I adjust the screw.

 

:panic:

[Guest cnas122]

Sorry to rehash an old thread, but I just got a new Colt Commando 12.5".  I use it with a can.  I've had plenty of SBRs with suppressors, but the gas and crud that hits my face is horrible.  Sometimes I look in the mirror and my face is black.  This is the first SBR I've owned that had this type of gassing problem.  It doesn't help that I'm a lefty.  Based on replies to this thread, am I correct that the adjustable gas block is the way to go and I should forego any thought about a heavier spring and buffer?     I have a 6.5" KA Rail so I would probably want to install my front sight on the gas block (any suggestions?).

 

Also (and I apologize if this has been asked before)....who is a good (or the best) gunsmith in Nashville to do the work.  I can do basic mods to my guns but I want a professional to install the block.  Some I have seen online are attached with bolts and I want mine peened.  I could try it myself, but I want it done properly.

Edited May 20, 2014 by cnas122