Feed issue

[pilot1695]

Hi there
I built this ar 3 yrs ago. Spike upper, lower and BCG with DD barrel plus surefire muzzle and spike T2 buffer.
Almost always, after I shot about 80 rounds, PMC, a round will get jammed by the feeding ramp. I clear the ham, it's good for another 20 30 rounds and it Will jam again.
I thought it was caused by the acu wedge, so I took it out, but the problem still there. I brought it to the gun store I go to, and they don't even know what's the cause of it.
Can anyone point me some directions to fix the issue?
Thank you

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[JaPes]

Obvious questions that need to be asked, not being a smart-a.

1. The barrel and upper receiver have M4 feed ramps?

2. I assume that the barrel nut is set to a minimum 30 ft-lbs to a maximum 80 ft-lbs torque?

3. Has the rifle done this from the start when it was newly assembled, or did this start happening recently?

4. Does this happen with any other ammunition brand other than PMC?

5. Does this happen with all the magazines you use?

Now that that's done, and assuming there's nothing wrong with any of the above...

It shoots fine up to 80 rounds, then the round gets hung up on the feed ramp. You stop to clear the jam (however long it takes you), you can shoot another 20 rounds and get a jam.

Sounds like there's something going on when the barrel warms up. Maybe there's an issue with one metal surface heating/expanding at a different rate than another? Maybe there's some heat expansion differential between the barrel's feed ramp and the receiver's M4 feed ramp cut that causes the tip of a round to hang up?

I'll have to think about this some more. Just brainstorming right now.

 

[Waywatcher]

Start with MEAL.

Magazines
Extractor
Ammunition
Lubrication

What are you using for each?

 

[thecatch8]

check your star chamber......make sure it's clean and dry.

 

[pilot1695]

@JaPes, thanks for all the inputs. I have the M4 ramp lined up, but I didnt torque it to the requirement when I install the barrel, just a estimate. I run it only PMC with Pmag and it's been doing that since completion.
@waywatcher, Pmag, spike BCG, PMC and hopper 9 lube.


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[JaPes]

Borrow a beam type torque wrench and double check the torque on the barrel nut. That's where I would start.

 

[thecatch8]

@JaPes, thanks for all the inputs. I have the M4 ramp lined up, but I didnt torque it to the requirement when I install the barrel, just a estimate. I run it only PMC with Pmag and it's been doing that since completion.
@waywatcher, Pmag, spike BCG, PMC and hopper 9 lube.


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You didn't properly torque your barrel........and you're having issues?

 

[pilot1695]

Yeah......I admit it..... I m getting a torque wrench to adjust it. Will let you know if the problem is solved..


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[Waywatcher]

Yeah......I admit it..... I m getting a torque wrench to adjust it. Will let you know if the problem is solved..


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That's a good first step.

When you say Hoppes #9 for lube, are you using the Original Hoppes #9 (that smells so nice)? If so, it could be burning off and leaving you underlubricated as it is not an ideal lubricant for ARs.

In any case, make sure you use plenty of good lube. I prefer CLP but there are lots of good choices.

 

[Rastoff]

Yeah......I admit it..... I m getting a torque wrench to adjust it. Will let you know if the problem is solved..

When you do this adjustment, be sure you follow the correct procedure.

The barrel nut must be loosened first. This will require removing the gas tube. I know that is a pain, but if you don't do it, the torque value you get won't be right.

Just for the record, I don't believe your feeding issues are due to improper torque on the barrel nut. Accuracy issues yes, but not feeding issues. The barrel is keyed. It's nearly impossible to have the feed ramps misaligned.

 

[pilot1695]

Agree, I just can't figure it out. It is always the left side round got jammed from the Pmag. I mean since the 223 round are pushed fed down to the mag.


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[pilot1695]

Waywatcher, yeah, the good smell one. So it's not proper for ar?


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[JaPes]

It's a good cleaning solvent. It isn't a lube.

 

[Waywatcher]

Waywatcher, yeah, the good smell one. So it's not proper for ar?

No, it's not proper. A good AR lube should be more of a honey/cooking oil-like consistency. Hoppes #9's main ingredient is kerosene, which is not a lubricant. (It's a solvent.)

I have had great luck with Breakfree CLP; it is mainly a lubricant but it also has cleaning properties which, in my experience, helps keep carbon dissolved. I bought a gallon of it so the price per ounce was downright reasonable and I uses much as I want.

Try switching to a lubricant before your next range trip, and see how it goes.

 

[pilot1695]

CLP break free, right


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[JaPes]

If after checking the barrel torque and using Breakfree CLP for lube the problem persists, check your extractor.

 

[Mcwsky09]

Are you sure it is hanging up on feed ramp? versus short stroking or round not high enough up in the mag/magwell for the bolt to catch the back of the round. pics of the jam condition might be helpful.

 

[Mcwsky09]

Agree, I just can't figure it out. It is always the left side round got jammed from the Pmag. I mean since the 223 round are pushed fed down to the mag.


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Mine was doing that every round from the left - in my case it was the mag sitting too low and the lip being too thick such that the left side round would slip off the front of the bolt as it was closing resulting in a wedged round that appeared ti be stuck on the feed ramp but was in fact the back of the round dropping too far as the nose rode up the ramp for it to remain in contact with the bottom of the bolt. Inexpensive CAA mags - took my sanding wheel rotary tool and thinned out the lips on the left side and jams are way way down - had some that I though were caused by the brass catcher getting in the way but am thinking that maybe my reloads need to be just a bit hotter as I might be short stroking.

 

[pilot1695]

This is what I use for lube

And this is the proper one?

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[Waywatcher]

I use the liquid, but that should work fine. Don't be stingy with it.
Here is a lube guide:
(G means generous, L means light--Generous means enough to be spread around with a finger.)