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 Issue with stovepiping
Ar-Bret  [Team Member]
1/25/2012 10:43:15 PM
So,

I've been through a bunch of diag an here is the issue

Yep it's stove piping, every mag has two or more...

Tried different mags...normally pmags but tried gi and others..no change

Cmmg upper in 16" 5.56 only about 500 rounds

Tried many lowers. Follows upper every time. Have several ar's

Tried several different bcg and stays with upper not the bcg

Checked gas tube clear and gas block clear... Port is .099-.101 measured

Gas tube is lined great with gas key

So down to just upper and barrel...

What am I missing or what could it be.

Thanks in advance

b
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turb06le240  [Member]
1/25/2012 10:46:20 PM
Originally Posted By Ar-Bret:
So,

I've been through a bunch of diag an here is the issue

Yep it's stove piping, every mag has two or more...

Tried different mags...normally pmags but tried gi and others..no change

Cmmg upper in 16" 5.56 only about 500 rounds

Tried many lowers. Follows upper every time. Have several ar's

Tried several different bcg and stays with upper not the bcg

Checked gas tube clear and gas block clear... Port is .099-.101 measured

Gas tube is lined great with gas key

So down to just upper and barrel...

What am I missing or what could it be.

Thanks in advance

b


Did you try different ammo, what ammo are you using, I would say fouled ejector Pbut you swapped bolts, I would say too strong of a mag, but you swapped mags, ect ect ect... But ammo could be your thorn too..
Is this upper new? Is it dripping wet with lube? Everything else is working properly, the bolt locks back on the last round?
vbfg135  [Team Member]
1/25/2012 10:54:53 PM
http://www.ar15.com/forums/t_3_66/499617_Stovepiping_AR___Possible_fixes___pictures_.html




http://www.ar15.com/forums/t_3_66/261908_Stove_piping_Why_.html&light=stove|piping



http://www.ar15.com/forums/t_3_15/532564_Short_stroking_and_stove_piping_on_new_gun.html&light=stove|piping



http://www.ar15.com/forums/t_3_118/478495_11_5_BCM_Stove_Piping_Issues__Fixed_.html&light=stove|piping



http://www.ar15.com/forums/t_3_66/488470_Interestng_results__stove_piping.html&light=stove|piping
Dano523  [Moderator]
1/25/2012 11:24:12 PM
Rifle correctly cleaned (including the chamber with a chamber brush), and correctly lubed with CLP,
Need you to load a single round into a USGI SPEC mag, and fire for effect.
Did the bolt lock back on the bolt catch?


Next, pull the charging handle all the way back, and confirm that the face of the bolt does not retracts back past the back of ejection port.

Now pull via a spent case off the extractor, does the ejector pin move freely in the bolt face without binding, just with a lot of spring tension.

From there, pull the extractor out of the bolt, and run your finger nail down the face of the extractor claw/grabbing edge, then down the rim releif channel outside edges to check for milling burs. If you find burs, then remove such so the case can seat correclty in the channel, and so when the case goes to pivot off the extractor, it not caught on any burs there.


Lastly, could be a new/rough chamber, and in cases like this, adding a #60 O ring around the extractor spring will increase it's tension for break in until the chamber self polishes through live fire (read O ring will fall apart in about 500 rounds, and such is still needed, then change the extractor spring out to a extra tension unit).
Ar-Bret  [Team Member]
1/25/2012 11:53:08 PM
Originally Posted By turb06le240:
Did you try different ammo, what ammo are you using, I would say fouled ejector Pbut you swapped bolts, I would say too strong of a mag, but you swapped mags, ect ect ect... But ammo could be your thorn too..
Is this upper new? Is it dripping wet with lube? Everything else is working properly, the bolt locks back on the last round?


ok,

Yes tried two different rounds...both 855 and 193 federal lack city 2010 and 2011

Gun was dripping wet...then tried it wipped down

Its is a newer upper have had problem since new

Book does lock back correct.

B
Ar-Bret  [Team Member]
1/26/2012 12:01:23 AM
Originally Posted By Dano523:
Rifle correctly cleaned (including the chamber with a chamber brush), and correctly lubed with CLP,
Need you to load a single round into a USGI SPEC mag, and fire for effect.
Did the bolt lock back on the bolt catch?


Next, pull the charging handle all the way back, and confirm that the face of the bolt does not retracts back past the back of ejection port.

Now pull via a spent case off the extractor, does the ejector pin move freely in the bolt face without binding, just with a lot of spring tension.

From there, pull the extractor out of the bolt, and run your finger nail down the face of the extractor claw/grabbing edge, then down the rim releif channel outside edges to check for milling burs. If you find burs, then remove such so the case can seat correclty in the channel, and so when the case goes to pivot off the extractor, it not caught on any burs there.


Lastly, could be a new/rough chamber, and in cases like this, adding a #60 O ring around the extractor spring will increase it's tension for break in until the chamber self polishes through live fire (read O ring will fall apart in about 500 rounds, and such is still needed, then change the extractor spring out to a extra tension unit).


Yep,

Rifle cleaned. And lubed. Bcg seems to run freely.

Lock back every time mag empty.

Doesnt seem to go back of the ejection port.

Now I've swapped out the bcg from known good working from other rifle and no change to this upper.

I've also tried new bcg in as well still no change

Tried fa bcg from fail zero through standard palmetto bcg to others and no change on the upper at all.

It's got about 500 rounds through it..lbeen trying to break it in...and working on this issue for a bit...

B
EaZeNuTZ33  [Team Member]
1/26/2012 12:32:10 AM
Heavier buffer would be my next thing....


I was having similar issues with my CMMG .308 when shooting it suppressed. I added approx. 1oz of lead shot the the buffer and a spacer to the buffer spring to add some extra tension and limit BCG travel......basically I slowed the BCG down! Function went to 100%.

I now have a new AR10 buffer spring and 10oz rifle buffer on the way for this rifle to see if it will still run 100% suppressed using them in the place of my white trash mods.

I run Spikes T2 buffers in my LWRC and my 22" home brewed AR, and whatever LaRue sends in their 556 OBR rifles (I figure the PST was meant for suppressors right)....I think an H2 is in the OBR. I don't own a rifle with a carbine or H buffer.....and even my standard rifle buffer in my .308 is going to the wayside in short order!
Dano523  [Moderator]
1/26/2012 1:30:41 AM
Originally Posted By Ar-Bret:

Doesnt seem to go back of the ejection port.





Show me a photo of the face of the bolt to the ejection port window with the charging handle pulled as far back as you can.


The face of the bolt should stop about 1/4 to 3/8 in from of the back of ejection port, and not the bolt face flush with the back of the port.
turb06le240  [Member]
1/26/2012 7:07:46 PM
Which gas block do they have on there, I had a problem with an upper, they had this cheizo gas block that was poorly machined, I swapped it out and problem solved... My problem was fast fire ftf and sometimes it would stovepipe...
Dano523  [Moderator]
1/26/2012 9:57:27 PM
If the bolt is locking back on the catch after the last shot fired out the mag, stroking is correct, and coming down to why the spent case is ending back up the action.

So it comes down to either the spent case not sticking to the bolt face until end of stroke, the ejector not ejection the spent case off the bolt at rear stall, the extractor not letting go of the spent case as its being pivoted off the bolt face via the ejector, or the bolt face behind the back of the ejector port window, with the spent case being deflected back into the action off the ejection port back edge.
Ar-Bret  [Team Member]
1/27/2012 12:48:00 AM
Originally Posted By Dano523:
Originally Posted By Ar-Bret:

Doesnt seem to go back of the ejection port.





Show me a photo of the face of the bolt to the ejection port window with the charging handle pulled as far back as you can.


The face of the bolt should stop about 1/4 to 3/8 in from of the back of ejection port, and not the bolt face flush with the back of the port.


Ok,

Here is what I see.

When I pull the charging handle back all the way it is just in front of the port...but not much...like maybe 2 thousands.

Is this what you are asking?

Or when it's on bolt catch?

Also how would you adjust that?

B
Ar-Bret  [Team Member]
1/27/2012 12:50:49 AM
Originally Posted By Dano523:
If the bolt is locking back on the catch after the last shot fired out the mag, stroking is correct, and coming down to why the spent case is ending back up the action.

So it comes down to either the spent case not sticking to the bolt face until end of stroke, the ejector not ejection the spent case off the bolt at rear stall, the extractor not letting go of the spent case as its being pivoted off the bolt face via the ejector, or the bolt face behind the back of the ejector port window, with the spent case being deflected back into the action off the ejection port back edge.


Well,

I can see about these, but I've tried 4 different working bcg from other rifles of diff makes.

I usually run the fail zero bcg as of late, yes to many ar's

B

P.s. I've ordered some different buffers to maybe try out to help,

Not sure who suggested that but they are on order.

B
EaZeNuTZ33  [Team Member]
1/27/2012 1:07:33 AM
Originally Posted By Ar-Bret:
Originally Posted By Dano523:
If the bolt is locking back on the catch after the last shot fired out the mag, stroking is correct, and coming down to why the spent case is ending back up the action.

So it comes down to either the spent case not sticking to the bolt face until end of stroke, the ejector not ejection the spent case off the bolt at rear stall, the extractor not letting go of the spent case as its being pivoted off the bolt face via the ejector, or the bolt face behind the back of the ejector port window, with the spent case being deflected back into the action off the ejection port back edge.


Well,

I can see about these, but I've tried 4 different working bcg from other rifles of diff makes.

I usually run the fail zero bcg as of late, yes to many ar's

B

P.s. I've ordered some different buffers to maybe try out to help,

Not sure who suggested that but they are on order.

B


I got my 10oz .308 buffer in today (heavybuffers.com).....hoping to try it this weekend. I was dealing with the same issues when I mounted my suppressor. Explanation given to me was that the bolt was traveling too fast (could cause over travel) and the cartridges did not have time to clear the bolt effectively. My ejection pattern was 1 o'clock at best.....typically right at my right bipod leg when shooting prone. I occasionally would have a case that would get launched 7-8' out when shooting prone, always figured the bolt smacked it like a baseball bat when coming back forward.

Hopefully the heavier buffers work for you. I personally would start with the heaviest buffer possible, load one round and see if she locks back on the empty mag....if it does, grab a topped off mag and see if reliability is back to 100%.
Dano523  [Moderator]
1/27/2012 11:17:54 AM
Originally Posted By Ar-Bret:
Originally Posted By Dano523:
Originally Posted By Ar-Bret:

Doesnt seem to go back of the ejection port.





Show me a photo of the face of the bolt to the ejection port window with the charging handle pulled as far back as you can.


The face of the bolt should stop about 1/4 to 3/8 in from of the back of ejection port, and not the bolt face flush with the back of the port.


Ok,

Here is what I see.

When I pull the charging handle back all the way it is just in front of the port...but not much...like maybe 2 thousands.

Is this what you are asking?


B

Yep, that's what I wanted to know.

The problem is that the bolt face is going behind the back of ejection port when the buffer bumper compresses, and the spent case is being danced off the back of the ejection port window edge, thenand back into the action.

Correct fix is to relieve the end of the receiver extension so it can turned in a few more winds, Or as a temp band-aid, get a few fender washers that are just a hair smaller that the tube ID, pull the buffer and spring, drop them down the tube, then put the spring and buffer back in. This shims the back of the tube back stopping wall forward (same as shorting the tube) and will stop the bolt face at the correct relationship to the back edge of the port window. Again, your looking for the bolt to max out rearward about 1/4 to 3/8" in front of the ejection ports back edge on a full charging handle pull ,and which give the bolt plenty of movement back past the bolt catch for the catch work correctly as well.

wagonwheel1  [Member]
1/27/2012 7:54:09 PM
I understand the bolt to max. out 1/4 - 3/8" in front of the port window. All my AR's max. out flush and I've never had any issues with ejection.

So it seems this is a " possible problem" but not "always a problem". Is this right? Not sure if I understand this 100%.

Dano523  [Moderator]
1/28/2012 6:42:21 AM
Originally Posted By wagonwheel1:
I understand the bolt to max. out 1/4 - 3/8" in front of the port window. All my AR's max. out flush and I've never had any issues with ejection.

So it seems this is a " possible problem" but not "always a problem". Is this right? Not sure if I understand this 100%.



Yes, as the bolt comes back to the end of rearward stoke, the buffer dead blow effect kicks in, and with the face of the bolt stopped just in front of the ejection port, then the spent case is finally pivoted off the bolt face, clears the back of the ejection port and strikes the deflector on the out side of the receiver. If the face of the bolt is at or behind the back of the ejection port when it stops at its rearward path , then the spent case tags the ejection port back window edge, and becomes a guessing game of if the spent case gets angled out of the port,or back into the action off that edge.


Bottom line, just look at the back edge of the ejection port window, and if you have brass scrap marks to that edge, then the bolt is coming back too far.
Ar-Bret  [Team Member]
1/28/2012 10:41:08 PM
Ok,

Well I talked with cmmg and they sent a call tags for this upper...the gas port is way too big.

I've never built an upper...so...Nuff said.

But they are going to replace it with one with a gas port that hopefully will be much smaller than 100

So I'm sending it out Monday, missed ups today, but see where it gets for there.thanks for all the help

B
EaZeNuTZ33  [Team Member]
1/28/2012 11:07:24 PM
Originally Posted By Ar-Bret:
Ok,

Well I talked with cmmg and they sent a call tags for this upper...the gas port is way too big.

I've never built an upper...so...Nuff said.

But they are going to replace it with one with a gas port that hopefully will be much smaller than 100

So I'm sending it out Monday, missed ups today, but see where it gets for there.thanks for all the help

B


I got a chance to try a new 10oz buffer in my CMMG .308 and adjusted my gas port to be the most restrictive......100% function now. I have a feeling the gas port on my .308 is too large as well. I have a solution that worked for what I needed.....and that was to keep my super accurate barrel!
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