AR Extraction Issue

[mannydog]

I've got this relatively new AR, about 500 rounds through it, with never even a fart. Last week, using three different mags spent casings wouldn't eject. Not every one but every 5 or 6 rounds. The following round was jammed with the spent casing still in the breech. Checked it out in the field, no obvious cause of the failures, and brought it home and cleaned it up nice and looked real closely and found no signs of any physical damage that might cause tis problem. The only difference this time on the range was that I had lubricated the bolt carrieri a little heavier than I normally might have, on the advice of a friend. It wasn't sloppy wet but fairly wet. I've been busy ekeing out a living so I having been back to the range yet to see if it's just too much CLP. Anybody have any thoughts on this?

Thanks

 

[LoginName]

Not to nit-pick, but extraction and ejection are two different things, but from what you're describing ("spent casing still in the breech"), it sounds like an extraction issue... perhaps a weak or broken extractor spring or grunge in the extractor lip/groove.

 

[BossHarley]

As LoginName said. Remove the extractor/spring and clean real well - inspect to be sure not broken/worn.

J

 

[Gammon]

I have had similar problems with two DPMS barrels. The gun would function reliably when fired rather slowly but the cases would stick in the chamber after the barrel heated up. This would typically involve 30+ rounds of fairly rapid fire. I tried a new extractor and spring with no improvement. The problem turned out to be a rough chamber and the cure was polishing which took a couple of hours. As a result I have pretty much given up on DPMS barrels.

 

[mannydog]

I mis-spoke, it's definitely an extraction problem. Extractor & spring look fine. Gammon, this one is a DPMS also and problem occurred after putting a couple of mags through it rapidly. How did you polish the chamber?
Thanks.

 

[DevX]

The only difference this time on the range was that I had lubricated the bolt carrieri a little heavier than I normally might have, on the advice of a friend. It wasn't sloppy wet but fairly wet. I've been busy ekeing out a living so I having been back to the range yet to see if it's just too much CLP. Anybody have any thoughts on this?

Thanks

Run it wet. If its a DPMS, upgrade the extractor and get the gas key staked properly. You also might want to check to see if everything is within spec. DPMS isn't known for their quality and reliability.

 

[Gammon]

I mis-spoke, it's definitely an extraction problem. Extractor & spring look fine. Gammon, this one is a DPMS also and problem occurred after putting a couple of mags through it rapidly. How did you polish the chamber?
Thanks.

Sounds like the same problem I had. I used a wooden dowell that was a loose fit in the chamber. Cut a slot in one end to accept strips of emery cloth, wet/dry sand paper, and crocus cloth. The strips (I used 1/2 inch width) are placed in the slot and wound around the dowell; you have to experiment to get a tight fit in the chamber. The other end goes into the chuck of an electric drill. Run the drill at slow speed and work the abrasive up and down the chamber.

I started with 150 grit emery cloth and then went to 220 wet/dry, 300 w/d, 400 w/d, 600 w/d, and finally 800 crocus cloth. I also cleaned the barrel between grit changes; carb cleaner and compressed air. I then did a final chamber polish using a tight fitting wool bore mop (the bore mop can be attached to a piece of cleaning rod which will fit in the drill chuck) coated with jeweller's rouge followed by JB non imbedding bore paste. The final clean up is crucial as grit and polishing compound can get into all of the nooks and crannies in the chamber, barrel and upper. I used solvent and compressed air followed by a conventional bore and chamber scrubbing. This system has cured the extraction problem in two DPMS Barrels. Good luck.

 

[Gammon]

PS This system will not work with chrome lined bores and chambers.

 

[stinx]

Check the extractor. Remove it from the bolt,then drag it across your arm it should leave a light scrape on yoy arm if not its probablt in need of replacement. Check the extractor spring next, if its a carbine the spring should be 5 coils and the insert should be black or gold( Gold is the most recent) If its blue or a 4 coil spring, change it. Lastly replace the parts in question and get a viton oring to place around the extractor spring these things together will greatly improve the gripping force of the extractor. IN a pinch a number 60 oring will work but its not as resistant to gun cleaning chemical as the Viton oring. I had these same issues with sevral of My Depts bushmasters changing the above parts solved the issues. YMMV

 

[MassMark]

This would not be the first DPMS barrel with an improperly cut chamber - if that's the case. I'm curious as to whether your carrier key is properly staked - if at all and could be loose. I'm also curious as to what kind of ammo you're using...Running your gun wet is not likely the issue.

 

[mannydog]

The ammo in question was Remington 50 gr JHP. Lots of real good insight from you all, I appreciate it. This DPMS was my first AR and I picked it up last year when they were flying off the shelves. I'm hearing more lately about the downside of DPMS. And, of course, a good friend of mine just got a SIG 556 for a lot less than my DPMS and he's been busting my chops. I'm going to get this straightened out but I can't even look at it till the weekend. Any more thoughts or suggestions, let it fly. I'll keep you informed.

Thanks, mannydog