ar-15 short stroking

shrxfn · Apr 11, 2017

Good luck man. The only other thing I could think of would be carbon deposit in the gas tube. maybe you could take it off and run something down it or some compressed air to see if there is a blockage but the 3 O'clock ejection says this isn't an issue.

I have mostly mid-length gas on all of mine except for the shorty upper I bought for my suppressed SBR build. I am going to break that upper down soon and install the adjustable gas block and quick attach for the suppressor soon. Hopefully I don't run into any gas issues........

scooterj · Apr 11, 2017

This may sound stupid but make sure that your barrel isn't clocked one way or the other. If so, the gas tube could be cocked and not making a good enough seal in the gas key.

bigtattoo79 · Apr 11, 2017

shrxfn said:
Good luck man. The only other thing I could think of would be carbon deposit in the gas tube. maybe you could take it off and run something down it or some compressed air to see if there is a blockage but the 3 O'clock ejection says this isn't an issue.

I have mostly mid-length gas on all of mine except for the shorty upper I bought for my suppressed SBR build. I am going to break that upper down soon and install the adjustable gas block and quick attach for the suppressor soon. Hopefully I don't run into any gas issues........

I have blown air though it and I feel there's nothing in it.

Good luck on the suppressed SBR build!

scooterj said:
This may sound stupid but make sure that your barrel isn't clocked one way or the other. If so, the gas tube could be cocked and not making a good enough seal in the gas key.

I will double check that but keep in mind the 1st 500rounds rain fine in this gun.

homeslice · Apr 11, 2017

When you blow air through it, are you blowing from the gas key side, or the gas port side? I assume that because it's able to eject but not pickup that there's a gas leak somewhere. Maybe the gas block has become misaligned with the gas port on the barrel?

bigtattoo79 · Apr 11, 2017

homeslice said:
When you blow air through it, are you blowing from the gas key side, or the gas port side? I assume that because it's able to eject but not pickup that there's a gas leak somewhere. Maybe the gas block has become misaligned with the gas port on the barrel?

I'm blowing in though the barrel. The gas block is pinned on so I'm not sure how it could move.

TheBigRServices · Apr 11, 2017

If you take the buffer and spring out and slowly cycle the action feel for any sort of resistance. Really the bcg should just fall all the way back if the trigger is reset. But I would dry fire and cycle with the action still with the spring out and lower attached, maybe something up with the trigger hammer binding and not wanting to reset.. cant think of how but thats all I can think of now.

John_ · Apr 11, 2017

When you grow weary of suggestions (a couple flat goofy) and can't remedy it, before you ship it to S&W, PM Magdump here on the forum and see if he will take a look at it/test fire it. Close to Hammond, Mag is the experienced and well versed witch doctor of all things AR related. He can exorcise your demons

bigtattoo79 · Apr 11, 2017

TheBigRServices said:
If you take the buffer and spring out and slowly cycle the action feel for any sort of resistance. Really the bcg should just fall all the way back if the trigger is reset. But I would dry fire and cycle with the action still with the spring out and lower attached, maybe something up with the trigger hammer binding and not wanting to reset.. cant think of how but thats all I can think of now.

I will look at it tonight.

John_ said:
When you grow weary of suggestions (a couple flat goofy) and can't remedy it, before you ship it to S&W, PM Magdump here on the forum and see if he will take a look at it/test fire it. Close to Hammond, Mag is the experienced and well versed witch doctor of all things AR related. He can exorcise your demons

Now that I have access to another rifle I hope to narrow it down this weekend. If not I will send him a PM.

SMR412 · Apr 11, 2017

I have a factory built Sig M400 that would run 100% on 5.56 ammo but would short stroke on some weaker .223 ammo.
I chased my tail for a bit. Finally measured the gas port, it was .053". Drilled it up to .06something and has run on everything since.
Have you compared quality 5.56 to known weak .223?

bigtattoo79 · Apr 11, 2017

SMR412 said:
I have a factory built Sig M400 that would run 100% on 5.56 ammo but would short stroke on some weaker .223 ammo.
I chased my tail for a bit. Finally measured the gas port, it was .053". Drilled it up to .06something and has run on everything since.
Have you compared quality 5.56 to known weak .223?

Great point and I have ran into the same problem with .223 in the past.

In this situation I'm using .223 from the same case that first ran great and have swapped to quality .556 with no difference.

bigtattoo79 · Apr 22, 2017

So without a doubt it's the bolt carrier causing the problem. The gas key is tight so once I get home I will clean it good and inspect it closely.

bigtattoo79 · Apr 22, 2017

Problem solved: Broken screw for the gas key.

BigP623 · Apr 24, 2017

bigtattoo79 said:
Problem solved: Broken screw for the gas key.

Good to see you found the culprit. Short stroking is almost always something related to gas.

bigtattoo79 · Apr 24, 2017

BigP623 said:
Good to see you found the culprit. Short stroking is almost always something related to gas.

I was thinking it was gas related. I will say the gas key would not wiggle at all and the screw head was held in place by the staking. Explains how the problem just started all of a sudden tho.

Thanks to everyone that offered some help!

shrxfn · Apr 24, 2017

Glad you got back on and let us know what it was. I have seen many threads were someone will ask for help and then disappears and you never know what did it.

I may be in the same boat soon I just swapped two uppers to adjustable gas blocks and have not had time to function test to see if I did the swap right.

SMR412 · Apr 24, 2017

Thanks for letting us know.

TheBigRServices · Apr 27, 2017

shrxfn said:
Glad you got back on and let us know what it was. I have seen many threads were someone will ask for help and then disappears and you never know what did it.

I know right?! Your like "Alright this is exactly whats happening to mine.." get to page 10.. nothing. "SOB!"

shrxfn · Apr 28, 2017

TheBigRServices said:
I know right?! Your like "Alright this is exactly whats happening to mine.." get to page 10.. nothing. "SOB!"

Exactly. I frequent a motorcycle forum and the same thing happens. Everyone spends days trying to help the OP who then disappears and you never know if someone was able to help or not........ So aggravating.

On a side note I got to test my 16" upper after doing the adjustable gas block swap and it only took me two tries to dial it in. On another forum I am on they talked a lot about adj gas and suppressors so I set it out to three clicks from closed. Got bolt hold open first try. Went one click closed shot and no hold open. Went back to 3 clicks open and got the bolt to hold open. All done with suppressor mounted as I will not be firing without one on a rifle again.

bigtattoo79 · Apr 28, 2017

shrxfn said:
Exactly. I frequent a motorcycle forum and the same thing happens. Everyone spends days trying to help the OP who then disappears and you never know if someone was able to help or not........ So aggravating.

On a side note I got to test my 16" upper after doing the adjustable gas block swap and it only took me two tries to dial it in. On another forum I am on they talked a lot about adj gas and suppressors so I set it out to three clicks from closed. Got bolt hold open first try. Went one click closed shot and no hold open. Went back to 3 clicks open and got the bolt to hold open. All done with suppressor mounted as I will not be firing without one on a rifle again.

Glad it worked out for you!

shrxfn · Apr 28, 2017

Me too I hate troubleshooting gas issues.

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