AR15.Com Archives
 Symptoms of overgassed gun
BamaInArk  [Team Member]
10/12/2010 12:05:27 AM
I've got a gun I assembled using a Spikes upper with a lower I assembled(Spikes stripped lower, etc). Carbine length gas system using a BCM BCG and an H buffer.

I am thinking this gun is overgassed. I'm wondering what all the symptoms would be for an overgassed gun.

I have posted about the issues with this gun before. Basically I'm getting 1:00 ejection no matter what ammo I use. When shooting off a bench half the ammo lands on the bench so it's easy to retrieve. lol Most of the suggestions from my previous post was to don't worry about it. It feeds any ammo I run through it. BCG not dragging on the hammer.

I finally got an H3 buffer to try out and see if that moves the ejection toward to rear a bit. I finally got to go shooting today. Well it still ejects at 1:00- 2:00 but now it just ejects them farther out. lol BUT....the last ammo I tried was some Monarch steel. When firing this it now ejects at about 4:00. So it seems the heavier buffer had the desired effect at least for the weaker loaded ammo. All the brass I shot today, several XM-193 loads, Q3131A1 and Monarch brass all eject at 1:00 to 2:00 o'clock.

I did notice something new on the brass today however. Getting ejection dings on the same spot on every single brass round that was fired. I didn't have the H buffer to try and see if that was eliminated. Also noticed I'm not getting any ejection marks on the flat part of the brass deflector. Only see wear at the corner where the receiver is milled to the flat part of the brass deflector. I'm not sure if that's normal or just another sign it might be overgassed.

I'm still not sure if the rounds are simply being bounced forward after striking the brass deflector.




Paid Advertisement
--
a308garand  [Team Member]
10/12/2010 12:32:12 AM
Your ejector spring is good and strong.
Your extractor is doing a good job.

Mess around with cutting a coil or so off of your ejector spring. Also think about how much extractor tension you are running,,,,,do you have a black extractor insert, new extractor spring and o-ring???? Dump the o-ring and see what happens. Your brass is all dented up because the extractor is holding onto the brass until it is struck by the edge of the ejection port!

Tuning the buffer helps to control/manage bolt bounce, but not so much with wicked hard casings being thrown out of the rifle like a guided missile.

Ease up on the extractor tension and or cut a coil off of your ejector spring.......

edit: I just looked at the photos again.,,,too much extractor tension.
AR-Performance  [Dealer]
10/12/2010 12:53:02 AM
Take your BCG out, slide a case under the extractor groove and straighten the case in the bolt face, let off slowly. does the case stick in the bolt face?
Extractors are a pain in the rear to make and hold in fixtures while being machined, I checked one batch of 100 Colt extractors the other day, there was .013" difference in the location of the groove form one extractor to another. apx 15% of the extractors were short and would cause the problems you report. 11% of this batch were longer than spec so apx 74% were in spec.

It could be the case sticking in the bolt or it could be that it is over gassed, loosen the gas block, spin it sideways a very small amout and shoot it, if it doesn't ding the cases and ejects later then you know it's over-gassed.
DKlic6  [Team Member]
10/12/2010 1:02:20 AM
Mine did this for about the first 1.5 k I put through it. It has worked itself out.
BamaInArk  [Team Member]
10/12/2010 1:43:48 AM
Further info:

When I first assembled the gun I didn't notice any ejection issues however I'm not sure if I just didn't pay attention or something changed.

I first noticed the problem after I replaced the standard charging handle with a new BCMGunfighter CH. I was shooting with a friend who had his Spikes SBR. We took his charging handle and put in mine to see if that made a difference. We then took his Spikes ST-T2 buffer and replaced the "H" buffer I was using. No difference. We then took his whole BCG and replaced mine...same ejection issue. So I've more or less eliminated those parts as a possible cause. I do have spare BCGs available but just haven't tried them as I thought I kinda eliminated those two parts...at least the bolt. I might try a new buffer spring. Maybe I got a funky one.

The BCM BCG was newly installed in this build. I am not using the o-ring. The barrel also has the standard FSB so I won't be able to loosen the gas block to see about changing the gas discharge pressure. Oh and I've also checked to see if the carrier key might be hitting the gas tube. Free and smooth.

What has me more concerned now is the way it's dinging brass. I don't think it did that with the "H" buffer but that seems contrary to the way a heavier buffer should work. Plus when you're shooting at a range the brass is flying in front of you where all the other crap shell casings are located. Harder to find and pickup your own brass! lol

And in case you missed it in my topic post the steel cased Monarch ammo ejects right where it should at about 4 to 5 o'clock. That to me is saying the lower powered stuff, i.e. less gas discharge, is just about right. Plus there are no case dings on the steel but that could be because the steel is harder so not seeing any marks.

That Ejection chart pic that is floating around has some suggestions for overgassed guns. The only thing I haven't tried is the SSS spring and an adjustable gas block which I guess I can't do anyway due to the FSB. The BCM carrier is the heavier auto one I'm pretty sure unless an M16 carrier is even heavier.

And as mentioned perhaps I just need to shoot it more!
TonyAngel  [Member]
10/12/2010 3:28:43 AM
I'm unclear as to whether you assembled the upper, or you bought a complete Spike's upper and assembled the lower and threw them together. If you built the upper, what barrel did you use. Check the inside of your upper where the cam pin rubs the receiver to unlock the bolt. Is it developing and wear channel? Like a gouge? I don't mean just rub makes, but metal being scraped away? It sure sounds like your rifle is over gassed and I think that the better ejection pattern that you getting with the steel cases ammo supports this.

Is your build such that you could swap out the gas block? You might want to try an adjustable gas block and see if you can turn down the gas and see if that helps. Do you have a clamp on gas block or maybe one held on with set screws? If it is possible on your build, maybe you could move your gas block forward a teeny bit to where you are obstructing a little of the gas port.
Gatorhunt  [Team Member]
10/12/2010 3:35:21 AM
I'm sorry if I missed it but I didn't see where you said what kind of barrel it was. Could be the gas port in the barrel is a little on the large side and sending to much gas back to the receiver. I would try and get my hands on an H2 or H3 buffer and see what happens.

ETA ... BCM BCG and M16 BCG is the same.
raygixxer89  [Member]
10/12/2010 5:17:28 AM
My deflector looks exactly like yours,OP. I've only shot a few rounds of q3131a1 but was unable to check my brass. I've mostly shot steel cased through it though.
It's a DelTon middie upper with I guess a standard carbine buffer/spring set-up. I can't remember the exact angle of ejection.
BamaInArk  [Team Member]
10/12/2010 2:35:18 PM
It was a Spikes complete M4 upper. I only assembled the lower.

I already mentioned changing from an "H" buffer to "H3" to test different buffers.

Standard pinned FSB(Front Sight Base) so no twisting it.
Gatorhunt  [Team Member]
10/12/2010 2:42:53 PM
I would almost bet a paycheck the gas port is over sized by .001" or .002" and letting to much pressure back to the receiver ... an H2 or H3 buffer should solve the problem ... did you contact Spikes yet ... I bet they would hook you up.
CONKLE73  [Team Member]
10/12/2010 3:07:57 PM
Originally Posted By BamaInArk:
It was a Spikes complete M4 upper. I only assembled the lower.

I already mentioned changing from an "H" buffer to "H3" to test different buffers.

Standard pinned FSB(Front Sight Base) so no twisting it.


Am I missing something…
You say it is a complete Spikes M4, but you are using a BCM BCG?

Didn’t your upper come with a Spikes BCG?
Onslaught  [Team Member]
10/12/2010 3:18:20 PM
PRI FatBoy gas tube?
BamaInArk  [Team Member]
10/12/2010 3:35:35 PM
Originally Posted By CONKLE73:
Originally Posted By BamaInArk:
It was a Spikes complete M4 upper. I only assembled the lower.

I already mentioned changing from an "H" buffer to "H3" to test different buffers.

Standard pinned FSB(Front Sight Base) so no twisting it.


Am I missing something…
You say it is a complete Spikes M4, but you are using a BCM BCG?

Didn’t your upper come with a Spikes BCG?


Yep...complete Spikes upper. I never used the supplied Spikes BCG. It's a spare now. Used the BCM BCG when the build was completed. I actually had the upper for over 6 months before I put it on the new lower I built.
CONKLE73  [Team Member]
10/12/2010 4:25:38 PM
Originally Posted By BamaInArk:
Originally Posted By CONKLE73:
Originally Posted By BamaInArk:
It was a Spikes complete M4 upper. I only assembled the lower.

I already mentioned changing from an "H" buffer to "H3" to test different buffers.

Standard pinned FSB(Front Sight Base) so no twisting it.


Am I missing something…
You say it is a complete Spikes M4, but you are using a BCM BCG?

Didn’t your upper come with a Spikes BCG?


Yep...complete Spikes upper. I never used the supplied Spikes BCG. It's a spare now. Used the BCM BCG when the build was completed. I actually had the upper for over 6 months before I put it on the new lower I built.


Not trying to be a smart ass, but why not use the BCG that came with, was head spaced with and was tested in that upper?
Thefryzone  [Team Member]
10/12/2010 5:41:27 PM
My Noveske N4 Basic Light, Colt SP1, and Double Star 16" HB carbine all eject at 1 to 2 o'clock and I have never had a problem. Back in the late 80's my SP1 would eject at 5 o'clock and hit lefties in the head but not anymore. I use Colt BCG's in all 3 of my AR's. As stated before buy other people. Don't fix it if it aint broke.
M4quadrail  [Member]
10/12/2010 5:57:52 PM
Other then the location of ejected cases and your dings are there any other signs of overgassing? Do you have an F marked FSB or Gas Block?
M4QUADRAIL
j3_  [Team Member]
10/12/2010 6:05:38 PM
Try a new mil spec ejector spring. A short spring can cause the 1 o'clock problem but over gassed can do it too.
Thefryzone  [Team Member]
10/12/2010 6:20:00 PM
Originally Posted By j3_:
Try a new mil spec ejector spring. A short spring can cause the 1 o'clock problem but over gassed can do it too.


What? BCM doesn't use mil spec ejector spring.
a308garand  [Team Member]
10/12/2010 6:50:48 PM
I still vote that he is getting too much extractor tension. The extractor is not letting go of the case and allowing the ejector to push the casing off of the bolt face until the casing is struck against the edge of the ejection port.
raygixxer89  [Member]
10/12/2010 8:59:28 PM
Originally Posted By a308garand:
I still vote that he is getting too much extractor tension. The extractor is not letting go of the case and allowing the ejector to push the casing off of the bolt face until the casing is struck against the edge of the ejection port.


I don't think it's the extractor because my upper has the exact same wear mark on the deflecter. I tried loading up a dummy round and it was ejecting as soon as the tip of the round cleared the lugs.
Unless our uppers are so over-gassed that bolt is flying back so fast as to cause the dent in the case?

ETA: OP,have you tried hand cycling a case and sees what happens?
waynewal  [Team Member]
10/12/2010 10:27:07 PM
Having the same problem with my DS Arms upper and a RRA bolt and BCG.
j3_  [Team Member]
10/12/2010 10:34:42 PM
Originally Posted By Thefryzone:
Originally Posted By j3_:
Try a new mil spec ejector spring. A short spring can cause the 1 o'clock problem but over gassed can do it too.


What? BCM doesn't use mil spec ejector spring.

Not sure but if you put a new one in your SP1 it will probably go back to the 5 o'clock it used to be before the spring shortened from use and taking a set.

SuperiorBarrels  [Dealer]
10/12/2010 11:06:14 PM
How is any of this a problem?

Your rifle feeds, fires, and ejects without malfunction. It works.
azoutdoorsman  [Member]
10/12/2010 11:11:19 PM

Originally Posted By SuperiorBarrels:
How is any of this a problem?

Your rifle feeds, fires, and ejects without malfunction. It works.

Yup. If you reload and dont want to ding up the brass, but a piece of sticky velcro (loop portion) on the deflector.
Fields_Overseer  [Member]
10/13/2010 12:43:30 AM
my stag did this also, I may get an extra power spring for the action. It will help the overgas issue and increase relability (up to 120%?)
jesse2205  [Member]
10/13/2010 2:04:27 AM
It is definitely the extractor spring. My larue stealth does the exact same thing. My brass kicks out at 1-2:00 and my brass deflector is wore just like yours with dings in my brass at the same spots as well. I emailed laure tactical and they said it is completely normal and there is nothing to worry about. I highly doubt your gun is overgassed. If you can't get it out of your mind, I would loosen up on the extractor spring and I bet that'll fix it.
Richard257  [Team Member]
10/13/2010 11:58:05 AM
Originally Posted By SuperiorBarrels:
How is any of this a problem?

Your rifle feeds, fires, and ejects without malfunction. It works.


Colt and LMT had figured out not to deflect brass off the corner of the deflector.
Others, the also-rans have not.

The problem is that OP does'nt like his brass sliced in half and does not wish
to peen the deflector.




chewbacca  [Team Member]
10/13/2010 12:04:25 PM
Try extra power buffer spring.
SuperiorBarrels  [Dealer]
10/13/2010 12:19:44 PM
Originally Posted By Richard257:
Originally Posted By SuperiorBarrels:
How is any of this a problem?

Your rifle feeds, fires, and ejects without malfunction. It works.


Colt and LMT had figured out not to deflect brass off the corner of the deflector.
Others, the also-rans have not.

The problem is that OP does'nt like his brass sliced in half and does not wish
to peen the deflector.


My two Colt and one LMT tacgot rifles do exactly the same thing as the OP's rifle. The rifles feed, fire, and load without malfunction; bullet hits where rifle is aimed. The rifles do what they are designed to do. Seems much to do about nothing.
BR870  [Member]
10/13/2010 1:13:45 PM

Originally Posted By SuperiorBarrels:
Originally Posted By Richard257:
Originally Posted By SuperiorBarrels:
How is any of this a problem?

Your rifle feeds, fires, and ejects without malfunction. It works.


Colt and LMT had figured out not to deflect brass off the corner of the deflector.
Others, the also-rans have not.

The problem is that OP does'nt like his brass sliced in half and does not wish
to peen the deflector.


My two Colt and one LMT tacgot rifles do exactly the same thing as the OP's rifle. The rifles feed, fire, and load without malfunction; bullet hits where rifle is aimed. The rifles do what they are designed to do. Seems much to do about nothing.
Agreed. My two Colt 6920s have wear on the same spot of the deflector( front edge). Its not ejecting to 1:00 though. More like 3:00...

GenoDinah  [Member]
10/13/2010 1:26:43 PM
Temporarily switch out the BCM with the Spikes BCG and see if you still have the same problems.
gtmtnbiker98  [Member]
10/13/2010 1:52:45 PM
Originally Posted By Richard257:
Originally Posted By SuperiorBarrels:
How is any of this a problem?

Your rifle feeds, fires, and ejects without malfunction. It works.


Colt and LMT had figured out not to deflect brass off the corner of the deflector.
Others, the also-rans have not.

The problem is that OP does'nt like his brass sliced in half and does not wish
to peen the deflector.




My 6920 has the same wear as most other ARs that are actually used. Go figure.

BamaInArk  [Team Member]
10/13/2010 3:44:50 PM
First off thanks for the responses. I will say however that some are making suggestions to things I've already posted about and tried.

@SuperiorBarrels....While I generally agree that it does shoot fine so why worry. The problem is 1st dinging the brass, which it shouldn't do and 2nd, as I mentioned in another post, when you're sitting at a bench on a well used range and your brass flies in front of you it get's mixed in with all the junk brass that get's left behind. Makes it harder to pick up you're own brass. Plus I do believe that a 1 o'clock ejection is simply an indication that something is not quite right with the gun and at least worth looking into. Which is what I'm doing.



I went shooting again today and brought one of my extra ARs. It's a Bushmaster ORC carbine with 1:9 twist. Nothing fancy except I have replaced the Bushmaster BCG in this gun with a Young chromed BCG(not a NM model).

1st thing I did was shoot the problem gun with the "H" buffer back in it. I wanted to see if that reduced the dings in the brass that I was seeing using the "H3" buffer. The only thing that changed with the "H" buffer was instead of spitting the brass out a distance the brass seemed to just "plop" out slightly in front at 1 o'clock. Pretty anemic ejection if you ask me. Maybe a foot away. Brass was still being dinged but not as much. I guess I must have missed the brass dings when I first assembled the gun and had been shooting it. I then tried the "carbine" buffer I took out of the Bushy lower and pretty much got the same thing.

Someone asked why I wasn't using the Spikes supplied BCG that came with the upper. Well I brought it today to try it out. It might have fired/ejected slightly better but basically it did the same thing as the BCM BCG I was using.

So I decided to use parts from the other gun to see how things looked. After trying the carbine buffer I then simply changed lowers. I put the Bushy carbine lower onto the "issue"(not gonna call it problem gun) gun. Right off the bat it ejected much better. Was ejecting at about the 3 o'clock. I thought that odd since the carbine buffer didn't work as good in the "issue" gun but all seemed to work better with the completely different lower. I went to change buffer springs but as I had them both out I ended up getting confused which one came out of which gun so stupid me couldn't really decide if that had been an issue or not. lol There was however a slight length difference in the springs.

I eventually took the Young chromed BCG from the Bushmaster upper and tried it in the Spikes upper and it appears it likes the Young BCG much better than either the BCM BCG or the Spikes BCG that came with the Spikes upper. I didn't try swapping bolts out of the carriers to see if that made a difference. I tried different buffers using the Young BCG and I could get ejection to move around based in which buffer I used...carbine, "H", and "H3". Don't have an "H2" buffer.

I even tried the BCM BCG in the Bushmaster using the carbine buffer and got brass ejection at 2 o'clock and steel at 5 o'clock while the same BCG in the "issue" gun ejects all at 1 o'clock.

At first I was using Monarch brass 223 but I eventually used it all up and then used a combination of XM193 and Monarch steel. I would load a mag with 2 M193 and 2 steel alternating in the mag. I would fire one round and notice how it ejected and then noticed how the other ones did alternating between brass(xm193) and steel. Using the Young BCG I was able to watch the rounds eject differently depending on how hot the round that was fired was even if changing buffers. But if I tried that in the using the BCM BCG I would get consistent 1 o'clock ejection with the exception of using steel with the "H3" buffer which ejected at about 4 to 5 o'clock.

Based on these tests I would say there's something about the Spikes upper that doesn't like the BCGs that I had used on it but seems to like, at least the one, Young chromed BCG I tried. Is it overgassed? Could the gas hole be slightly oversized? I don't know but for the time being I'm gonna move the Young chromed BCG to this gun. I'm about the strip the upper on the Bushmaster anyway and install a new BCM barrel. Guess I'll just used the BCM BCG in this upper and hope it will work ok.

Also some other thoughts.....why does one lower seem to change ejection pattern? Spring or buffer differences? Carrier dragging on hammer? I didn't notice an dragging.
Richard257  [Team Member]
10/13/2010 11:01:29 PM

Brass from Noveske N4.


I had similar dings from Armalite middy.
Cases would eject at 1:00 o'clock in both rifles with those machete cuts in the middle.

H3 buffer or extra power spring alone did not improve anything, especially in Noveske.
Wolff extra power spring and H3 buffer together changed the ejection to 4-5 o'clock in both guns.

I will try different extractors, extractor and ejector springs, remove o-rings,
do modifications to those springs as suggested by other members,
to see if ejection pattern will change without having to use extra power recoil springs.


fatkid35  [Team Member]
10/14/2010 8:03:46 PM
if your still thinking overgassed,you could always move your fsb and check your gas port size. i just bought a m4 barrel in the white from jp surplus. had to drill my own gas port. looked up the specs and made mine .062 to start off with. seemed small but it cycled great. i also have a 16 in. pencil barrel with a rifle lenght gas system. had to make the port .093 before it cycled reliable. check your port size to see what you got going on there. my other 16 in. barrel has a carbine lenght system and port size of .074. feel a bit more recoil than the m4 but kicks brass out at 4 o'clock like normal.

edit: just noticed the last sentence in your last post. my non hooded carrier did not like my bobbed hammer in cmmg lower i have. had to use hooded carrier with that lower. the notched hammer worked fine with the non hooded carrier. by hooded i mean the firing pin was covered more at the back by the carrier.could notice the difference pulling back the charging handle.one would drag for a second, the other slid smooth. swapped parts in different uppers and got same results.
Paid Advertisement
--