AR failure to feed help

[tommyfly]

so im suspecting short stroking, but wanted to run my information through the forums for some second hand opinions.

first, my specs.
Rifle is a home build with all PSA parts (minus the stripped lower)

PSA dissipator upper
PSA LPK, including spring and buffer

my rifle generally shoots good for ~10 shots, then starts having feeding issues. The used case always ejects successfully. the follow us cartridge then either doesn't feed at all, or gets caught mid way up the ramp.

Perfect example is shown at the 0:28 and 0:36 second mark of this video:

https://www.youtube.com/watch?v=bL808lxdEsA

also, bolt sometimes fails to lock back after shooting the final round

for remedies, I have tried multiple different mags, as well as two different kinds of brass case ammo (PMC bronze and some other unidentified factory xm193)

i also tried the search bar without luck

I dont really know where to go from here, so help would be appreciated,
and thanks ahead of time for any feedback.

[solislbc]

I was having the same issues. I loosened the mag catch and tapped the magazine everytime I load. Solved my issues.

[scotty99]

My first guess would be mag related. Were all the mags you tried the same brand? If you load a single round and fire, does the bolt lock open? If so, that usually means gas is ok. Did you assemble the upper or buy it already built? Does it have an adjustable gas block?

If you have a friend with a good working AR, try your upper on his lower with his mags. If that works, you can be pretty confident the upper is not the issue.

Lastly, PMC Bronze ammo is the worst I've ever shot. I have four ARs and none of them liked it. Try at least a box or two of better ammo to see if it functions any better.

How many rounds through this gun?


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[nate76239]

I thought I saw on a thread a while back it could be the gas key on the bcg, takes a while to heat up then starts gas leak. I made a thread where my issue was due to gas leak at the gas tube/gas block. I replaced the gas tube and no malfunctions afterwards.

http://www.calguns.net/calgunforum/showthread.php?t=1031683

[tommyfly]

My first guess would be mag related. Were all the mags you tried the same brand? If you load a single round and fire, does the bolt lock open? If so, that usually means gas is ok. Did you assemble the upper or buy it already built? Does it have an adjustable gas block?

If you have a friend with a good working AR, try your upper on his lower with his mags. If that works, you can be pretty confident the upper is not the issue.

Lastly, PMC Bronze ammo is the worst I've ever shot. I have four ARs and none of them liked it. Try at least a box or two of better ammo to see if it functions any better.

How many rounds through this gun?


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i tried different mags, mil surplus and pmags, all of which feed fine in other rifles. Mags was my first thought also

the upper came assembled from the factory. I checked around the gas blocks and there was evidence of minor leakage, but nothing serious that i havent seen on other rifles

probably a few hundred rounds through the rifle at this point. Its hard to break it in when it jams every other shot.

Ill try switching uppers and lowers around with my brother next time were out, and ill also try to pick up some 5.56 and see if that helps it cycle.

Ill try everyone else's tips also, Thanks for the advice

[codypaint77]

so im suspecting short stroking, but wanted to run my information through the forums for some second hand opinions.

first, my specs.
Rifle is a home build with all PSA parts (minus the stripped lower)

PSA dissipator upper
PSA LPK, including spring and buffer

my rifle generally shoots good for ~10 shots, then starts having feeding issues. The used case always ejects successfully. the follow us cartridge then either doesn't feed at all, or gets caught mid way up the ramp.

Perfect example is shown at the 0:28 and 0:36 second mark of this video:

https://www.youtube.com/watch?v=bL808lxdEsA

also, bolt sometimes fails to lock back after shooting the final round

for remedies, I have tried multiple different mags, as well as two different kinds of brass case ammo (PMC bronze and some other unidentified factory xm193)

i also tried the search bar without luck

I dont really know where to go from here, so help would be appreciated,
and thanks ahead of time for any feedback.

First always ensure the rounds are all seated by tapping the magazine.
Second make sure your bolt gas rings are not lined up together, they should be spaced.

[Mail Clerk]

so im suspecting short stroking, but wanted to run my information through the forums for some second hand opinions.

first, my specs.
Rifle is a home build with all PSA parts (minus the stripped lower)

PSA dissipator upper
PSA LPK, including spring and buffer

my rifle generally shoots good for ~10 shots, then starts having feeding issues. The used case always ejects successfully. the follow us cartridge then either doesn't feed at all, or gets caught mid way up the ramp.

Perfect example is shown at the 0:28 and 0:36 second mark of this video:

https://www.youtube.com/watch?v=bL808lxdEsA

also, bolt sometimes fails to lock back after shooting the final round

for remedies, I have tried multiple different mags, as well as two different kinds of brass case ammo (PMC bronze and some other unidentified factory xm193)

i also tried the search bar without luck

I dont really know where to go from here, so help would be appreciated,
and thanks ahead of time for any feedback.

tommyfly,

Based on your description I believe for sure you have a gas leak that's coming from the carrier key.

Try using another BCG and see what happens. I'll bet you need to replace the carrier only and not the bolt itself.

Mail Clerk

[golfish]

PSA makes some good stuff, its a Mid-length Gas System, right?

Did you take apart the gas block and check everything out? make sure there's no burrs ? Oh!! you probably have the F front sight. Could be something caught up in the gas system making things slow down a bit.

Please keep us up to date on what your fix was..

fish

[jkody]

Check to make sure the gaps in the gas rings are not lined up too.

[m850168]

If the gas rings are lined up, and staggering fixes it, then there are deeper problems with the rifle. A properly set up AR should run fine with one gas ring.

[baih777]

Short stroking. As mentioned above check the gas key. Make sure the bolts are tight and no leakage. Then remove the bolt and check the gas rings. If all looks good then check the gas block. Make sure the bolts are tight. Make sure the gas block and barrel gas port are alined.

[fmunk]

so im suspecting short stroking, but wanted to run my information through the forums for some second hand opinions.

first, my specs.
Rifle is a home build with all PSA parts (minus the stripped lower)

PSA dissipator upper
PSA LPK, including spring and buffer

my rifle generally shoots good for ~10 shots, then starts having feeding issues. The used case always ejects successfully. the follow us cartridge then either doesn't feed at all, or gets caught mid way up the ramp.

Perfect example is shown at the 0:28 and 0:36 second mark of this video:

https://www.youtube.com/watch?v=bL808lxdEsA

also, bolt sometimes fails to lock back after shooting the final round

for remedies, I have tried multiple different mags, as well as two different kinds of brass case ammo (PMC bronze and some other unidentified factory xm193)

i also tried the search bar without luck

I dont really know where to go from here, so help would be appreciated,
and thanks ahead of time for any feedback.

1. Check your bullet button device, if it's too tight, it might be just enough to allow the magazine to seat but not fully—making the follow up round too low and the mag follower too low to engage BHO.
2. If the above check out fine, check your feed ramps. Do they look normal? are they aligned correctly?
3. Next up, gas block and gas port. It could be under gassed.

I would say #1 is most likely culprit.

[tommyfly]

i always tap the mags, checked the gas rings, and everything is lubed properly.

so right now for range remedies i have down that i should try:

-higher power ammo
-different BCG
-loosen mag catch
-upper on a different lower+different mags

If that fails ill pull stuff apart and inspect the gas tube.
if anyone has any other ideas i could add to the list, it would be appreciated.

i should get out to the range eithor this weekend or next, ill let everyone know how it goes.

Thank you all for the input

[fmunk]

Loosen your mag catch first before you waste time and ammo. It's free and quick.

[Agent 0range]

Tagged. I've been experiencing similar issues with a newer build with an 80% lower and PSA complete upper. Just loosened the mag catch and can't wait to see if that fixes it.