Try taking a piece of toilet tissue, one square should be enough. Fold it in half and use tweezers, needle nose pliers, whatever you have at hand to push one end through the hand guard, around the gas tube, and back out the other side. Wrap as necessary to cover the gas block to gas tube joint completely. Fire a round. If you've got a gas leak it will be obvious.
DPMS AR15 Ejecting but not picking up next round
- Thread starter homeslice
- Start date
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Cajun Camper
Well-Known Member
Is he using factory ammo or reloads?
We tried 2 different types of ammo, American Eagle 223, and Federal "green tip" XM855 I think. But I'm confident we've found a gas leak with the gas tube into the gas block at this point, I just need to make time to take the hand guard off and check into it.
The gas block to barrel and gas tube to gas block "connections" are not sealed. There will be leakage around these areas which stands out against a shiny stainless surface like a gas tube or unfinished stainless barrel. Below is a picture from ARFCOM showing someone with a similar concern on a pistol that is functioning fine. I chose this picture because the stainless steel barrel and gas tube makes it easy to see and because it appears to be a 7.5" barrel with pistol length gas which will exaggerate the observed effect. This would be way more leakage than I would like to see on a 16" mid length setup. You'll see more extreme examples of this on the cheaper AR15s and home builds since they do not pay much attention or hold as tight of tolerances for the gas block ID and/or barrel OD dimensions. A lot of times the residue will semi-seal the mated surfaces over time as you shoot it.
In regards to the issue in the OP, if this is an issue the gun has always had, to me the problem seems like an over gassed gun. Maybe the reason why the person sold it. Looking at the casing in your picture, if the marring on the casing you are referring is the marring located on the lower 1/3 of the case then it looks like the it runs the entire length of the case. Some symptoms of an over gassed gun can be not stripping rounds, not locking back on last round, bolt bounce and the bolt not fully seating due to bolt bounce sending it into battery, bouncing back and not having enough energy to return into full battery. Remedy this issue with an H or H2 buffer weight.
If the rifle has been working fine for a while and suddenly developed this issue I would agree it is probably under gassed due to something coming loose or a blockage.
In regards to the issue in the OP, if this is an issue the gun has always had, to me the problem seems like an over gassed gun. Maybe the reason why the person sold it. Looking at the casing in your picture, if the marring on the casing you are referring is the marring located on the lower 1/3 of the case then it looks like the it runs the entire length of the case. Some symptoms of an over gassed gun can be not stripping rounds, not locking back on last round, bolt bounce and the bolt not fully seating due to bolt bounce sending it into battery, bouncing back and not having enough energy to return into full battery. Remedy this issue with an H or H2 buffer weight.
If the rifle has been working fine for a while and suddenly developed this issue I would agree it is probably under gassed due to something coming loose or a blockage.
tallwalker
Well-Known Member
That'll do it! Glad you got it squared away.
machinedrummer
Well-Known Member
Ain't got no gas. In my best Carl (sling blade) voice. Glad it's up and running again.
Glad it got fixed!!!
I recently ran into a similar problem, waiting to happen. A buddy had me swap the handguards over to a free float tube on his Ar. So I had to remove the fsb so he could cut it down to clear the tube. He had shot a fair amount of 22lr through it, using a drop in conversion. Lead shavings from the 22lr bullets had completely filled the port on the barrel, the gas block and had got about 1/4 inch into the gas tube. Took quite a bit of work with a pick to clean everything.
Moral here? Gas ports can clog, and having a dedicated 22lr upper is likely a good idea.
I recently ran into a similar problem, waiting to happen. A buddy had me swap the handguards over to a free float tube on his Ar. So I had to remove the fsb so he could cut it down to clear the tube. He had shot a fair amount of 22lr through it, using a drop in conversion. Lead shavings from the 22lr bullets had completely filled the port on the barrel, the gas block and had got about 1/4 inch into the gas tube. Took quite a bit of work with a pick to clean everything.
Moral here? Gas ports can clog, and having a dedicated 22lr upper is likely a good idea.
Sounds like classic under gassing to me. And the residual noted at the gas block does indicate a leak where one should not exist. I've seen gas tubes fracture and form a split right at the gas block starting at one of the pin holes and or the gas hole. Also, those tubes are supposed to fit snug inside the block. If for some reason it's not snug it will leak and you will notice the gas escape through the handguard when shooting.
Otherwise, the gas hole in the barrel may need a good reaming. When you consider it's around .06 inches in diameter, it's not exactly the path of least resistance with any sort of fouling. I have never seen a gas tube become occluded to the point of blockage.
Otherwise, the gas hole in the barrel may need a good reaming. When you consider it's around .06 inches in diameter, it's not exactly the path of least resistance with any sort of fouling. I have never seen a gas tube become occluded to the point of blockage.
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