Brand new AR feeding issues. *problem solved*

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Before anyone says "take it back" its 100% a custom build, so with that out of the way heres the problem.

I finally got the chance to take my AR out today and fire its first shots. 1st mag, 1st round failed to feed..bolt comes about halfway forward (it started to feed the round) and that was it, pulled back on the charging handle and let go, it chambered. It went "bang" ejected the round and did the same thing on the next round...basically it keeps doing this. So it grabs the round, starts to feed it...then stops.

I started off with a crappy old preban hicap mag I had, luckily I was shooting in NH and my friend had PMAGS he let me use....it did the same thing. (side note, his "off the shelf" gun OCCASIONALLY did this to, but not every round like mine"

I was @ MFL so I asked if there was anyone there that could possibly spare the time and take a look at it, luckly one of the guys working behind the counter said he would. First off he said it was a little to dry for a brand new rifle and soaked the crap out of the thing (from all my reading I didn't know they needed to be as wet as he made it). It freeded it up a little, now it would only do it every other round. At one point I got so frustrated with my new expensive single shot AR that I rapid fired it...and it worked flawlessly for the 15 or 20 rounds left in the mag. And it does lock back on an empty mag(another thing that leads me to believe its not a short stroke problem)

Also the guy shooting next to our party said he said the SAME problem with his AR and once it got broken it (1000 rounds he said) it seemed to fix itself. He also said that polishing his M4 feed ramps made a difference.

Now from what I understand this isn't a short stroking problem because that would re chamber the previously spent caseing which isn't my issue. I found a few people online via a google search saying it could be the hammer dragging on the BCG (will investigate that tomorrow). So any possible imput here would be extremely helpful. The crappy part is I dont often get the chance to get to a range where I can fire a rifle to do any quick live fire tests. And here are some quick specs that could be of use to anyone that could have an idea..

16" carbine length gas system w/ a rifle length stock...and it is a rifle length spring and buffer in the tube.Both the Upper and barrel are cut w/ m4 feed ramps. Daniel Defense lower parts kit, BCM full auto BCG...and i was shooting Federal XM193.

Thanks in advance to anyone who helps me out with this one.
 
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Get a chamber brush and vigorously clean chamber. I had a new ar that was doing the same thing, cleaned chamber and has been running fine.
 
Just a FYI. Run it wet. AR's like that. I use Mobil 1, soak the BCG, shake it off and blast away (That is, after you figure out what's causing the short cycle).

Sounds like there is some sort of obstruction that is preventing the bolt to move freely. If you manually cycle the bolt do you feel any resistance? Cycle it slowly and feel for resistance. If there is no resistance, examine the feed ramp.

Once you get it sorted out, you'll love the rifle.
 
who's barrel?

Did it only have problems when the mag was full?

Does the BCG cycle smoothly by hand?

Is the gas block aligned correctly? Is the gas block tight against the barrel shoulder or off slightly?
 
who's barrel?

Did it only have problems when the mag was full?

Does the BCG cycle smoothly by hand?

Is the gas block aligned correctly? Is the gas block tight against the barrel shoulder or off slightly?

delton barrel

no, pmags or regular mags, @ any capacity from full to 1 round left

it felt like it did when i did the bench tests before i took it out

and its gotta be, i used the gas block that came on it, so its pinned in place


im off to my dungeon to tear this thing apart now, if the problem continues i will post a video. will try and post an update before the superbowl starts
 
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and its gotta be, i used the gas block that came on it, so its pinned in place. im off to my dungeon to tear this thing apart now, if the problem continues i will post a video. will try and post an update before the superbowl starts

That doesn't mean they pinned it with the right alignment and that the gas port is the correct diameter.
 
Before anyone says "take it back" its 100% a custom build, so with that out of the way heres the problem.

I finally got the chance to take my AR out today and fire its first shots. 1st mag, 1st round failed to feed..bolt comes about halfway forward (it started to feed the round) and that was it, pulled back on the charging handle and let go, it chambered. It went "bang" ejected the round and did the same thing on the next round...basically it keeps doing this. So it grabs the round, starts to feed it...then stops.

I started off with a crappy old preban hicap mag I had, luckily I was shooting in NH and my friend had PMAGS he let me use....it did the same thing. (side note, his "off the shelf" gun OCCASIONALLY did this to, but not every round like mine"

I was @ MFL so I asked if there was anyone there that could possibly spare the time and take a look at it, luckly one of the guys working behind the counter said he would. First off he said it was a little to dry for a brand new rifle and soaked the crap out of the thing (from all my reading I didn't know they needed to be as wet as he made it). It freeded it up a little, now it would only do it every other round. At one point I got so frustrated with my new expensive single shot AR that I rapid fired it...and it worked flawlessly for the 15 or 20 rounds left in the mag. And it does lock back on an empty mag(another thing that leads me to believe its not a short stroke problem)

Also the guy shooting next to our party said he said the SAME problem with his AR and once it got broken it (1000 rounds he said) it seemed to fix itself. He also said that polishing his M4 feed ramps made a difference.

Now from what I understand this isn't a short stroking problem because that would re chamber the previously spent caseing which isn't my issue. I found a few people online via a google search saying it could be the hammer dragging on the BCG (will investigate that tomorrow). So any possible imput here would be extremely helpful. The crappy part is I dont often get the chance to get to a range where I can fire a rifle to do any quick live fire tests. And here are some quick specs that could be of use to anyone that could have an idea..

16" carbine length gas system w/ a rifle length stock...and it is a rifle length spring and buffer in the tube.Both the Upper and barrel are cut w/ m4 feed ramps. Daniel Defense lower parts kit, BCM full auto BCG...and i was shooting Federal XM193.

Thanks in advance to anyone who helps me out with this one.

I rented the lane next to you guys.... (I was in #12. ) (Maybe it wasn't you, but there was someone in #13 who was constantly re-jacking rounds in their AR for like an hour, so what are the odds ) BTW my head still hurts, j/k.... everything you brought was loud. [rofl]

BTW, rifle buffer? That might be half the problem.

-Mike
 
heres the update....mind you its doing this without firing so i really don't think in my completely amateur opinion its gas system related...

ok before i took it apart i slowly pulled the charging handle back and felt for any resistance....

right about here i feel it start to drag
IMAG0697.jpg

and its 100% dragging on the hammer

ok fine, maybe it is the hammer. So I went ahead and removed it, threw the 2 snap caps in the only magazine I have. I tried releasing the bolt via the catch in the locked back position, and charging it with the handle with the bolt foward. Both methods worked and it fed flawlessly.

Ok so i figured i'll load up the magazine and cycle it 30 times to see if it does it agian.

1st round, full magazine (HAMMER REMOVED)
IMAG0700.jpg


and it continues from there, no matter the capacity in the magazine it does this....if you pull the changing handle from there, it will chamber it. Pull again to simulate a shot and it will come forward and jam like that again....

here are some more pictures
IMAG0701.jpg


IMAG0702.jpg


Thats the frustrating part, when I function tested it with the dummy rounds when I completed the build it functioned flawlessly, but apparently this rifle is racist towards live ammo.

so im starting to think now its a magazine issue....like I said yesterday with PMAGs it still did it just not as much (every OTHER round)
 
I rented the lane next to you guys.... (I was in #12. ) (Maybe it wasn't you, but there was someone in #13 who was constantly re-jacking rounds in their AR for like an hour, so what are the odds ) BTW my head still hurts, j/k.... everything you brought was loud. [rofl]

BTW, rifle buffer? That might be half the problem.

-Mike

ahaha no crap, yep that had to of been you, thanks for the info you gave me yesterday

I guess people went kidding when they said a battlecomp tends to annoy people shooting around you...

and as for the Mosin my shoulder is still killing me from shooting that...


and for the last part, i thought your supposed to use a rifle buffer in a rifle length tube to matter what gas system...[thinking]
 
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I'll guess it's an out of spec lower and the mag is seating a little low. Try cycling while pushing down on the mag (pushing the mag into the gun) or even try it by removing the mag catch and pushing down on the mag (like on a bench).
 
Based on what you have said, position of the bolt when you feel resistance and it dragging on the hammer, I think Tackdriver nailed it (no pun intended). Lower sounds out of spec.
 
Based on what you have said, position of the bolt when you feel resistance and it dragging on the hammer, I think Tackdriver nailed it (no pun intended). Lower sounds out of spec.

[sad2] does anyone have any measurements i can take of it? My best friends uncle is a mechanical engineer and a fellow firearms enthusiast who has a thing for measurements. I know he would break out micrometers and calipers to compare the spec measurements to mine.
 
First things first. A carbine length gas system needs a carbine length spring and a heavy buffer. Make sure you installed the DD lpk correctly. Who manufactured the upper? M4 feed ramps do not need polishing. Are you sure you have them?
 
Try switching the upper. This will at least tell you which half the problem should be in. I shoot a Harvard frequently. You are welcome to join me next time I am there to try one of my uppers it if you do not have another.

Dave
 
First things first. A carbine length gas system needs a carbine length spring and a heavy buffer. Make sure you installed the DD lpk correctly. Who manufactured the upper? M4 feed ramps do not need polishing. Are you sure you have them?

Bad info, a carbine length gas system upper(or any other length gas system upper) will run fine with a rifle tube buffer and spring. I have many and they run flawless this is NOT the problem with this rifle.
 
1. Does not look like a gassing issue at all. Appears to be BCG bindng on "something."
2. That "something" could be:
a. Mag seating too high (BCG binding on the mag lips).
b. Mag seating too low (cartridge binding on feed ramp/mag lips stopping BCG)
c. BCG binding in buffer tube
d. BCG binding in upper.
e. cartridge catching on bad feed upper/barrel extension feed ramp.

Here's what I'd start looking for:
1. I can't see if the bullet is caught on the feed-ramp/barrel extension interface. Is that smooth? See any copper building up there or dings on the tips of your bullet?
2. Try the upper on a good lower and the lower on a good upper. If binding goes away then:
a. If good upper works with your lower, then mag seating _should_ be ok.
b. If good lower works with your upper, then mag seating is likely the issue.
c. If good lower still fails with your upper, then you are back to all the issues with feed ramp, buffer tube, BCG/upper binding.
3. Look closely for any wear marks on the rear of the BCG or the buffer tube for binding there. The Buffer tube is relatively soft metal compared to the hardened BCG, so it will show wear first, shine a light in that puppy.
4. Look closely in the bottom of the charging handle and inside top of the upper for any indication of binding there.
5. Look closely at the inside left of the upper where the bolt retainer/cam pin would ride if it were out of spec.

Also, recognize that the trigger itself is going to provide some resistance as you pull back. The BCG is cocking the hammer so pushing it down against the hammer spring. There will be a point charging stroke where you feel that tension.

Sounds like you have banged it around enough that you should find some scuff marks or burrs somewhere...

Good luck...
 
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1. Does not look like a gassing issue at all. Appears to be BCG bindng on "something."
2. That "something" could be:
a. Mag seating too high (BCG binding on the mag lips).
b. Mag seating too low (cartridge binding on feed ramp/mag lips stopping BCG)
c. BCG binding in buffer tube
d. BCG binding in upper.
e. cartridge catching on bad feed upper/barrel extension feed ramp.

Here's what I'd start looking for:
1. I can't see if the bullet is caught on the feed-ramp/barrel extension interface. Is that smooth? See any copper building up there or dings on the tips of your bullet?
2. Try the upper on a good lower and the lower on a good upper. If binding goes away then:
a. If good upper works with your lower, then mag seating _should_ be ok.
b. If good lower works with your upper, then mag seating is likely the issue.
c. If good lower still fails with your upper, then you are back to all the issues with feed ramp, buffer tube, BCG/upper binding.
3. Look closely for any wear marks on the rear of the BCG or the buffer tube for binding there. The Buffer tube is relatively soft metal compared to the hardened BCG, so it will show wear first, shine a light in that puppy.
4. Look closely in the bottom of the charging handle and inside top of the upper for any indication of binding there.
5. Look closely at the inside left of the upper where the bolt retainer/cam pin would ride if it were out of spec.

Also, recognize that the trigger itself is going to provide some resistance as you pull back. The BCG is cocking the hammer so pushing it down against the hammer spring. There will be a point charging stroke where you feel that tension.

Sounds like you have banged it around enough that you should find some scuff marks or burrs somewhere...

Good luck...

FANTASTIC info....it actually led me to discover what I believe is the problem.....

I started to go through this checklist, checked out the buffer tube and only found this wear.

IMAG0706.jpg

that doesn't seem that bad, so I continue the search...

IMAG0707.jpg

bottom of the BCG..theres more wear on one side but nothing crazy

the search continues


[
IMAG0708.jpg

little wear around the gas key...once again nothing crazy

IMAG0710.jpg

feed ramps seemed fine just a little dirty

so at this point, I filled a mag and started trying the pushing up on the bottom test like cekim said to try

blah blah blah...anyway...it was feeding...hummmmmmm

the mag was filled with 10 rounds and it kept functioning perfectly...would load the first round then pulling back on the handle it would eject and feed the next....then it started to act up agian....


....then i noticed it, which explains every OTHER round....it jams feeding from the LEFT side of the magazine

did a few more tests and noticed when the left hand side round is the next to load. it sits like this

IMAG0709.jpg

SLIGHTLY angled up, drop the bolt from there...it jams. If i stick my finger in and level it, it chambers.


so i dunno if its a bad magazine or the bolt catch is messed up, because it was doing this with the PMAGs too....at least i thought it was...I cant really remember if I used any after the guy @ MFL soaked the bolt for me

Tomorrow my coworker is going to bring his magazines to work for us to try out

so maybe case closed for now
 
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ok another update

Tried my upper on a differnt lower, still jamed (left side only)

Tried 4 different mags, still jamed (left side only)

SOOOOOOOOO by process of elimination it has to be the left side feed ramp, right?
 
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