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View Full Version : Can upper reciever wear cause a failure to feed?



CallMeShooter
11 June 2009, 07:46
I am having a problem running one of my guns, and was wondering if upper reciever wear could be part of my problem. I can see what looks like wear inside the upper reciever along where the top of the carrier runs, which makes my carrier move rough by hand.
First, my gun is set up with a mid length DI gas system on a sabre 16" 1 and 7 chrome lined barrel and a LMT bolt and carrier. I am guessing I have around 6K rounds through the gun and all shot through a suppresor. Here lately I have been having a problem getting my gun to feed correctly, and my carrier feels rough when cycling. The round is actually hanging up on the feed ramps or it seems to be, but I am not sure my carrier is operating fast enough. I can clean it thoroughly which helps, but within 100 rounds after cleaning I start having problems again. I am running the bolt and carrier slightly lubed.
After I clean the upper, bolt and carrier and reassemble the carrier still feels rough inside the reciever. Is this totally a carrier related problem or could reciever wear be contributing to the malfunction. And how many rounds will an upper reciever last? Any feedback would be appreciated.

Stickman
11 June 2009, 10:34
I doubt that the receiver is worn enough in 6,000 rounds to cause any trouble. However, that doesn't change that something could have chunked and ground into your receiver. Not likely, but possible.

I would look at a few things, first and foremost, take the easy step of ripping it all apart, and giving it a good cleaning. Tear your BCG all the way down, check everything over. Once that is done, lube it up heavy and drop it back in. See if there continues to be a problem.

One of the things I would look for would be increased wear around the feedramps. If your feedramps are gouged, you are going to have problems.



Lastly, what lube are you using, and how much do you use? When running a can, the lube gets sucked up quick.

CallMeShooter
11 June 2009, 16:18
Thanks for the reply. I have regularly tore every thing down. I totally dissasemble the carrier (except for the gas key) and bolt to remove all carbon and carbon build up. I then lube and reassemble the bolt and carrier. I also thoroughly clean the inside of the upper reciever, chamber, and bore. I degrease, clean, then lightly lube the bore.
Stick, it does not look like my feed ramps are gouged any at all, that is just the most frequent spot the cartrige hangs when the gun fails to cycle completely. I am getting good extraction and ejection, it just feels like the carrier is lagging and loosing speed as it works.
Another thing is that this has only been giving me a problem on the last 4 to 5 hundred rounds. Now I have to thoroughly clean every hundred rounds not to have the problem, and before I could go 4 to 5 hundred rounds without any problems at all.
The oil I use is remington moisture gaurd, which has never given me any problems in any of my other AR's. I have used a grease for a little while, but ultimately stopped using it because I felt like it would gum up the gun faster than oil. The oil might be my problem, but I do run the gun pretty wet.

Eric
11 June 2009, 21:38
Specifically what kind of F/T feed are you experiencing?

Stickman
11 June 2009, 22:34
Specifically what kind of F/T feed are you experiencing?


I think thats the big question in my mind. The second biggest question would be why you are using moisture guard as your primary lube for the weapon.

IIRC, its a light weight lubricant designed mainly to prevent rust. A real lube should work better, though I'm not sure it would totally solve the problem. As Eric commented, we really need to get a little better intel.

CallMeShooter
12 June 2009, 06:04
The specific failure to feed is the actual cartridge stopping on the feed ramps as the carrier cycles. When it occurs all I do is pull the charging handle back and release which chambers the round.

I will try using a different lube. The only other I have on hand is the regular aerosol remington oil and a gunslick brand oil. In reading remingtons write up on the moisture gaurd it is made from remington oil with an added moisture protectant.

I will try a different lube and report back with the results.

CallMeShooter
12 June 2009, 06:06
I should get to shoot my rifle tonight, so when the problem occurs again I will try to get some pictures to help explain the problem.

I was able to shoot this afternoon, and here are the results. I did not clean my rifle after the last shooting session which was two nights ago. So I would have thought my problem would actually be worse, but I dumped three mags through it with only one failure to feed.

Something to think about is I did not lube the carrier before I shot, so I am wondering if I might be lubing it too much when the malfunction occurs. Previously when the gun would hang up I usually spray oil directly onto the carrier and bolt, then work the charging handle a few times to get me back running. Maybe I am causing additional fowling with the extra lube in the gun when it is hot, or not?

I guess since I was trying to force the problem the gun ran well. I am not the best camera man at all, but here are the few pics I took to demonstrate what is happening.

http://img146.imagevenue.com/loc190/th_50990_DSCN2261_122_190lo.JPG (http://img146.imagevenue.com/img.php?image=50990_DSCN2261_122_190lo.JPG) http://img7.imagevenue.com/loc901/th_51819_DSCN2262_122_901lo.JPG (http://img7.imagevenue.com/img.php?image=51819_DSCN2262_122_901lo.JPG) http://img186.imagevenue.com/loc600/th_52139_DSCN2263_122_600lo.JPG (http://img186.imagevenue.com/img.php?image=52139_DSCN2263_122_600lo.JPG) http://img211.imagevenue.com/loc411/th_52832_DSCN2264_122_411lo.JPG (http://img211.imagevenue.com/img.php?image=52832_DSCN2264_122_411lo.JPG) http://img207.imagevenue.com/loc347/th_53110_DSCN2268_122_347lo.JPG (http://img207.imagevenue.com/img.php?image=53110_DSCN2268_122_347lo.JPG) http://img227.imagevenue.com/loc474/th_53301_DSCN2272_122_474lo.JPG (http://img227.imagevenue.com/img.php?image=53301_DSCN2272_122_474lo.JPG)

jmart
12 June 2009, 21:35
If you are on your original buffer spring and you've gone 6K rounds, it's time for a new buffer spring.

spamsammich
13 June 2009, 04:30
You run your weapon too dry, with the wrong lubricant.

I'm of the opinion that you can't run it too wet, also clean your mags periodically, especially since you shoot suppressed.
http://vickerstactical.com/tactical-tips/weapon-lubrication/

Eric
13 June 2009, 07:35
Holy megapixel Batman! Look at downsizing the pics.
From what I can see, that weapon is way to dry and the buffer spring specs are 10 1/16" min to 11 1/4 max.

Give it a proper cleaning and lube, drop in a new spring and give it a go. If that does not cure it, we can look at other things.

CallMeShooter
14 June 2009, 05:10
Sorry about the pic size, I am new to posting pictures on the net. I will measure my spring and try a different lube. Thanks for the info.

Eric
14 June 2009, 08:23
Sorry about the pic size, I am new to posting pictures on the net. I will measure my spring and try a different lube. Thanks for the info. If you have an opportunity, give us an update after you run it again.
For photos, I like to use www.photobucket.com

cz777
14 June 2009, 19:31
please look at buffer/spring and bolt carrier alignment ? gas key /charging handle slot wear ? it looks like you running it too dry -what is the oil you are using ? mobil one 15w40 works very well .