weird experience with an ar-15

[maxmayhem]

i just finished a build on an ar 15...i took it to fire it...i had a brand new spikes bcg.....when i fired about 5 rounds through the thing it would not cycle....i just set it aside and figured i had not aligned the gas system correctly (when i installed it i just slid it on there and eyeballed it)....after i got home from the range...i lined it perfectly and check the gas tube and all checked out....i had a guy stand beside me and see if the bolt was moving all the way back which he said it did move --enough to spit out brass sometimes but never fully cycled) ..he also said it was shooting debris out of the chamber.....this made no sense to me and i watched him shoot it and saw the same thing....i got home and the bolt carrier had unnatural friction...i took it apart and the carrier had gunpowder/debris in and the bolt looked like the photo below...i was using normal ammo--american eagle...this has got me stumped...
this is a pencil thin spikes barrel and a new spikes bcg....fired less than 10 times (like i said above maybe 5 that i recall specifically)


i should also add that the bcg action is still tight and gritty even after cleaning the debris off it...i have a theory but i dont want provide it so i wont taint the theories of others

 

[Mgderf]

That looks magnetized to me, and it appears to have metal shavings hanging on.

 

[jblomenberg16]

Unburned powder is one potential cause, although when I've had it in my action it has been partially burned, and has a yellow / orange look to it. I see this sometimes when running suppressed.

If you have access to other ammo I'd give that a try and see if the issue stays with the ammo. Not to get you too alarmed just yet, but there are some rumors that AE has had some quality control issues. There have been a few "kaboom" threads where what seem to be rounds loaded with the wrong powder created over pressure. The extreme on the other side would be powder that is so slow to burn, that it just gets pushed out and then back into the action and chamber, as well as some going out the end of the bbl.

 

[Jwmeador]

i just finished a build on an ar 15...i took it to fire it...i had a brand new spikes bcg.....when i fired about 5 rounds through the thing it would not cycle....i just set it aside and figured i had not aligned the gas system correctly (when i installed it i just slid it on there and eyeballed it)....after i got home from the range...i lined it perfectly and check the gas tube and all checked out....i had a guy stand beside me and see if the bolt was moving all the way back which he said it did move --enough to spit out brass sometimes but never fully cycled) ..he also said it was shooting debris out of the chamber.....this made no sense to me and i watched him shoot it and saw the same thing....i got home and the bolt carrier had unnatural friction...i took it apart and the carrier had gunpowder/debris in and the bolt looked like the photo below...i was using normal ammo--american eagle...this has got me stumped...
this is a pencil thin spikes barrel and a new spikes bcg....fired less than 10 times (like i said above maybe 5 that i recall specifically)


i should also add that the bcg action is still tight and gritty even after cleaning the debris off it...i have a theory but i dont want provide it so i wont taint the theories of others

What exactly happened when it failed to cycle? There could be a gas leak. Are there any signs that could look like gas leaking out of the key? Is the gas key still tight?

 

[maxmayhem]

i dont think its amercan eagle as i used the rest of the whole box in four other ar-15s with no issues whatsoever.....i checked first for a gas leak...check the gas tube...no sign of burn marks near gas tube and gas block connection...gas key is good...the problem that I believe it has is that the carrier is a little too tight..it is difficult to pull the bolt in and out of the carrier manually--and i mean its stiff..this prohibits the bolt from cycling so would this happen if the typical gas would not operate the bolt?

 

[Jwmeador]

i dont think its amercan eagle as i used the rest of the whole box in four other ar-15s with no issues whatsoever.....i checked first for a gas leak...check the gas tube...no sign of burn marks near gas tube and gas block connection...gas key is good...the problem that I believe it has is that the carrier is a little too tight..it is difficult to pull the bolt in and out of the carrier manually--and i mean its stiff..this prohibits the bolt from cycling so would this happen if the typical gas would not operate the bolt?

Wow. So is the carrier oversized or is it the runway in the reciever? Have you tied a different carrier from another AR in the suspect rifle?

 

[maxmayhem]

that is my next step in order to isolate the bcg as the issue...

Wow. So is the carrier oversized or is it the runway in the reciever? Have you tied a different carrier from another AR in the suspect rifle?

 

[milton]

tagged for interest.

 

[rvb]

Pressure bleeds out the side of the carrier through the ejection port as the bolt unlocks. So that's not unusual. Sometimes hard to see, some times easy depending on powder, atmosphere (humidity etc), amount of oil getting blown out, etc.

If gas system is all lined up and good, it may just need some breaking in. Lube it good, esp the carrier race ways and the rings. Work it by hand or put 100 rounds through it with something a little hotter, eg m855. Make sure the cylinder inside the carrier is smooth. Make sure the carrier key is tight and sitting flush.

-rvb

 

[BGDave]

Looks like your gas rings and or the bolt at the gas ring diameter is out of whack. Could also be soft gas rings. Got those myself once from fly-by-night supplier.

 

[AmmoManAaron]

It should not look like that after only 10 rounds, that thing is filthy. I wonder if there was some sort of preservative somewhere in one of your new parts (gas tube?) that is getting burned and fouled? Or maybe like the poster above said, soft gas rings? All of that debris and filth is coming from somewhere.

 

[Psode27]

It should not look like that after only 10 rounds, that thing is filthy. I wonder if there was some sort of preservative somewhere in one of your new parts (gas tube?) that is getting burned and fouled? Or maybe like the poster above said, soft gas rings? All of that debris and filth is coming from somewhere.

I tend to agree, way too dirty for a few rounds. I'd clean it like crazy, lube it with your fav lube, and try it again.
The other side of my thinking leans toward tolerance stacking of some sort. could some part you have be on the fat or lean side of mil spec? happen to have any headspace gauges (I dont think thats the problem, just to rule out)? are you sure you have your gas block lined up on your gas port hole? While I agree it could be gas rings, they look intact enough to not cause issue. Not sure! good luck and keep us posted!

 

[maxmayhem]

negative....gas system is good...i think it is gas rings, bolt out of spec, or something to do with bcg...i will try and get out to the shooting range again but it is over 40 minutes away...probably be this weekend....

I tend to agree, way too dirty for a few rounds. I'd clean it like crazy, lube it with your fav lube, and try it again.
The other side of my thinking leans toward tolerance stacking of some sort. could some part you have be on the fat or lean side of mil spec? happen to have any headspace gauges (I dont think thats the problem, just to rule out)? are you sure you have your gas block lined up on your gas port hole? While I agree it could be gas rings, they look intact enough to not cause issue. Not sure! good luck and keep us posted!

 

[slickshot223]

Looks like the bolt is not unlocking fast enough to expel the carbon from the fired round, the buildup if any should be a carbon deposit just behind the gas rings on the bolt. The bolt should move freely in and out carrier with some resistance. Should not take extreme effort to move it!!
Check to make sure the carrier moves freely also, and that it is not sticking on the gas tube!

 

[maxmayhem]

i had not read this yet but this is what i did...i dont think the extractor was facing inward as i believe some brass came out (i dont even know this is possible)...i took it apart and swapped parts for a second with a working Bcg to check fit then switched back....then I put it back together...maybe i flipped the cam around or something but its as smooth as can be now and not binding like before...before and after this process i manually worked the bolt back and forth many tines but noticed the real difference when the reassembled it...it could have been debris or something causing the binding..i will test it soon and report back

Pressure bleeds out the side of the carrier through the ejection port as the bolt unlocks. So that's not unusual. Sometimes hard to see, some times easy depending on powder, atmosphere (humidity etc), amount of oil getting blown out, etc.

If gas system is all lined up and good, it may just need some breaking in. Lube it good, esp the carrier race ways and the rings. Work it by hand or put 100 rounds through it with something a little hotter, eg m855. Make sure the cylinder inside the carrier is smooth. Make sure the carrier key is tight and sitting flush.

-rvb

 

[maxmayhem]

This is correct..it should move freely with some resistance...i have built about 15+/- ar 15s so i knew the binding in the bcg was not normal...it seems normal now since i played around with it and i think its gonna be fine

Looks like the bolt is not unlocking fast enough to expel the carbon from the fired round, the buildup if any should be a carbon deposit just behind the gas rings on the bolt. The bolt should move freely in and out carrier with some resistance. Should not take extreme effort to move it!!
Check to make sure the carrier moves freely also, and that it is not sticking on the gas tube!

 

[Thumper]

Its gas rings.You should never have carbon on top of gas rings.The outer sealer surfaces should always be shiny

 

[maxmayhem]

May have been gas rings...may have been other things but its normal now...took it apart,oiled it ,manually operated bolt about 100 times, made sure extractor was facing the right way, and inserted cam pin opposite how it was ...it is now normal and im positive it will function correctly

Its gas rings.You should never have carbon on top of gas rings.The outer sealer surfaces should always be shiny