AR-15 Failure to Feed

Shawnyc

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So I have over one thousand rounds through my AR (10.5” SBR). I am now getting pretty frequent FTF where the round is jammed between the bottom of the bolt and the feed ramp. Also, the bolt doesn’t hold open on the last round.

Unfortunately I have changed two things simultaneously and I don’t know which one is the issue. I ran over one hundred rounds of 22lr through it using the CMMG conversion the last time out, and I installed a new Fail Zero nickel boron BCG.

At this time does it sound like the 22lr ammo gunked up the gas system causing the BCG to short stroke? Or is there an issue with the Fail Zero BCG.

I’m going to try to get to the range again tomorrow and run it with a milspec BCG.

EDIT: This occurs with multiple types of magazines.
 
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citoriguy

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I'd start with the BCG too. I have a couple FailZeroes and haven't had an issue, but many have had them of one kind or another.
 

Shawnyc

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Sorry forgot to add it happens with multiple types of mags. Will edit my post.
 

92G

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return to original BCG
fire with 1 round in mag
if fail to lock open, its undergassed
most common cause for this is gas block has shifted such that has tube no longer in alignment with port. I’m putting my money on this. I have had this happen. It’s common for those who actually shoot their rifle (as you’re doing).
 

SJan

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100 rounds of even the dirtiest 22 shouldn't be enough to gum up the gas port/gas tube. Even so, it is recommended to thoroughly clean after using a 22 conversion.

In your case it's probably the BCG that you changed. Other less likely cause is something worked loose in the gas block area. Is it a pinned block? Or a set screw style?
 
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Shawnyc

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In your case it's probably the BCG that you changed. Other less likely cause is something worked loose in the gas block area. Is it a pinned block? Or a set screw style?
It has a fixed FSP so it would be pinned.
 

xjma99

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It’s short cycling. I would swap to old or any other BCG and try again. It shouldn’t be but could very well be a gas issue. Thorough cleaning may just do the trick
 

Shawnyc

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Its ruined, 22lr is a killer!
Nooooo! That’s what I get for trying to save a few bucks. The CMMG kit is nice but the mag is what holds the bolt open, so using it for practicing reloads doesn’t work.
 

Uzi2

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The CMMG kit has a block between the 22lr bolt and buffer. Essentially the buffer tube doesn’t get used.
The GAS TUBE still gets shit in it from the .22 going down the barrel.

Flatten the end of a piece of 16ga steel wire and "roto root" the gas tube then run some .223 ammo through the gun.

Then check for gas key leakage on your new bolt carrier and run the rifle wet.
 

Uzi2

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The buffer tube the same for 22 lr and 556 ?
.22LR conversions are blowback operated, directly from their own chamber using their own small buffer spring.

They can foul a gas tube with unburned powder and lead as the bullet passes by the gas hole in the barrel.

The buffer tube is on the rear of the rifle.:)
 
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I would say unless you shot thousands of rounds of 22lr the gas tube is not blocked. Unless your gas port is shaving lead of the bullet.?
 

Uzi2

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I would say unless you shot thousands of rounds of 22lr the gas tube is not blocked. Unless your gas port is shaving lead of the bullet.?
By making a couple of hundred ( not thousands) lead shavings that would fit through a gas hole's diameter, I think you'd be surprised at the volume.
 
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By making a couple of hundred ( not thousands) lead shavings that would fit through a gas hole's diameter, I think you'd be surprised at the volume.
I put a cmmg insert on my stag during the ammo shortage. I burned up my oldest 22lr in the hoard. Aprox 3500 rounds. Never cleaned it ran fine.
Now a friend brought me his ar after 500 rounds and I plucked a chunk of lead out of the front sight port? I also have ran cast 224 bullets through my AR with zero issues.

Its all fun ,
 

Shawnyc

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Partial update. Couldn’t get to the range. Stripped and cleaned the gun, lubed it up good. Hand cycled mags of five snap caps. First mag hung up once. Hand cycled about twenty more mags of five snap caps with no issue. Now I’m thinking she was just dirty but a range test is coming this week.
 
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Translation (most likely anyway):

My gun is fouled from lack of cleaning after running garbage ammo, now it doesn't work right :)..

If a new round gets jammed between the bolt and feed ramp basically what is happening usually is the bolt isn't coming back far enough to catch the base of the cartridge, it's sweeping the round in from some other place..

Hand cycling a mag will prove proper ejection and feeding if you see this again. If that works ok you know your problems are related to gassing..

Also if the bcg isn't coming back far enough similarly it doesn't make it to the catch..

If you clean your rifles after every use this stuff doesn't happen.

Make sure the gas block or tube/pin hasn't somehow come loose. Spray out the gas tube with gun scrubber, clean everything until its spotless, double check your gas rings. Clean and inspect your buffer spring. Check operation..

If the same thing repeats try manually cycling, if that looks ok I'd probably replace the gas block and tube - basically the tube may be clogged and they are usually a bitch to separate from the gas block after awhile (and are cheap enough if nothing extravagant). Such will also isolate any problems if the gas block is out of alignment and allows you to inspect and clean the port in the barrel.
 
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If you clean your rifles after every use this stuff doesn't happen.
Gonna have to disagree. I ran my rifle, for almost the entire year without cleaning it. Around 3600 rounds. When I finally broke down and cleaned it it was still working fine. It was just insanely dirty. I was trying to run it til it failed. I broke down and cleaned it cause I was disgusted and embarrassed with how nasty it was.
 

Uzi2

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I put a cmmg insert on my stag during the ammo shortage. I burned up my oldest 22lr in the hoard. Aprox 3500 rounds. Never cleaned it ran fine.
Now a friend brought me his ar after 500 rounds and I plucked a chunk of lead out of the front sight port? I also have ran cast 224 bullets through my AR with zero issues.

Its all fun ,

You had a well drilled gas hole in the barrel with no burr. Some barrels have it.
Gonna have to disagree. I ran my rifle, for almost the entire year without cleaning it. Around 3600 rounds. When I finally broke down and cleaned it it was still working fine. It was just insanely dirty. I was trying to run it til it failed. I broke down and cleaned it cause I was disgusted and embarrassed with how nasty it was.
There's no future in running a dirty rifle. 😆
 
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If I cleaned my rifle everytime I shot it I would be cleaning ALOT. If im shooting a bunch i'll punch the barrel with a boresnake, wipe off the bolt and add lube. That will be good for a a case or two.
Exactly! I kept it well lubed and it ran perfectly. But like I said, it was incredibly dirty and kinda embarrassing.
 

Shawnyc

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The only gun I clean after every use is my carry gun. Typically it needs a cleaning anyway due to all the lint.
May hit the range tomorrow and will report in.
 

Uzi2

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If I cleaned my rifle everytime I shot it I would be cleaning ALOT. If im shooting a bunch i'll punch the barrel with a boresnake, wipe off the bolt and add lube. That will be good for a a case or two.
That's usually good enough and more than some do.( or don't do)
 
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Just because you can fill an AR15 with mud or run 5000 rounds without too many jams doesn't mean you can't dirty it beyond well operating, or prematurely wear it out. Its like smoking, only a small percentage actually get cancer but that doesn't mean smoking is unrelated.

As not only I indicated likely this rifle has a plugged gas system or something else gunked up.

One of the great things about an AR is they are easy to clean completely. If your rifle is kept up with it takes 20 minutes doing a fairly complete job and is a basic part of gun ownership really.

Sure if I shot mine every day I might clean it weekly but typically I shoot on Sunday - when I get home with an AR the upper is removed, BCG removed and stripped down, extractor and pins placed aside (because of the o ring), rest of BCG parts take a kerosene bath. Later on I spray out the upper, gas tube, and barrel with a solvent, cleanup any deposits, clean the chamber and barrel, swipe barrel with oil, scrub and solvent spray off the BCG parts, inspect/assemble/lube.. lower and buffer tube gets a spot cleaning and quick lubes, and it's put away in perfect condition... same with my pistols.

On a piston gun like a mini, or a shotgun that sees low round counts, I may just do the barrel and a once over to remove deposits without a full tear down but generally decent firearms are quick and easy to completely clean and they all work best that way IMHO.
 
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