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View Full Version : AR experts, please help diagnose...


SURVIVOR619
06-03-2012, 3:47 PM
Had these problems today, out of about 200 rounds, 10 of them had this dented case when chambering.. The bolt jammed with the round angled into the ramp..? Is the bolt cycling too quickly? This problem began after about 150 non-issue shots... Another oddity was that the bolt would not stay open on some of the last shots, yet with the next magazine would..? Tried again with the erred magazine and it held open next time..?..?..

Thanks in advance for helping an AR goon.

http://img.tapatalk.com/62b010c1-f783-e735.jpg

http://img.tapatalk.com/62b010c1-f795-7245.jpg


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repubconserv
06-03-2012, 3:49 PM
What ammo you got there?

SURVIVOR619
06-03-2012, 3:49 PM
BTW, these are Lake City reloads if that matters..

I'm using a standard carbine buffer in a 16" carbine upper.


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SURVIVOR619
06-03-2012, 3:54 PM
http://img.tapatalk.com/62b010c1-f945-0c5c.jpg


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SURVIVOR619
06-03-2012, 3:56 PM
That shot above is of two successfully fired and ejected rounds... Checking to see if any oddities with extraction (random scratches on bottom of case)..


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DarkSoul
06-03-2012, 4:00 PM
Did you reload the rounds? It looks like the rifle is short stroking, could be a few different things, could be ammo that's not hot enough, check your recipe (if you are reloading).

If it ran fine and as the day wore on it started to do this, possibly not enough lube on your rifle. Remember that ARs will run dirty, but they won't run dry.

SFgiants105
06-03-2012, 4:00 PM
As per usual, my first impulse is to ask if you tried using different magazines. I have come to hate metal constructed AR mags; I prefer composite. Anyway, it seems that the bolt isn't grabbing the round properly, which in my mind is a bolt problem (face, not carrier group) or magazine problem. Try using different mags with the same ammo, and if it happens again, use your current mags with different ammo.

If it still occurs after that, I guess you could try playing around with other things. It could be the buffer spring, or the bolt, or the BCG, or maybe the barrel isn't lined up properly. I've never seen any malfunctions like that.

Let us know what it ends up being; I'd be interested to know.

scobun
06-03-2012, 4:04 PM
Try different mags and different ammo as a first fix. My bet is on crappy mags. If the mag doesn't sit up high enough, the bolt won't catch enough of the case head when cycling. You'd have to have REALLY crappy mags to be that out of whack, but they're out there. Does your upper have M4 cuts? What about the barrel? Pictures of the extension and upper receiver fit will help.

That ammo looks terrible, btw. I'd try something different.

SURVIVOR619
06-03-2012, 5:41 PM
Yeah it is dirty brass... Shoots like a gem out of my AK... It could likely be a lube issue. I should've taken pics of the jams as they occurred.

I'm using magpul pmags from Midwest PX that are 20 rounders cut down to 10 and pinned...


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SURVIVOR619
06-03-2012, 6:03 PM
Ok more pics.. Any other thoughts? Looks to me like upper mates just fine with lower.. Yes, M4 feed ramps. Excuse the dirty... Haven't given her a cleaning yet... Thanks again anyone who may be able to assist..

Lower
http://img.tapatalk.com/62b010c1-1744-63aa.jpg


http://img.tapatalk.com/62b010c1-1782-df41.jpg


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SURVIVOR619
06-03-2012, 6:04 PM
Lower with upper...
http://img.tapatalk.com/62b010c1-17ac-3d3f.jpg


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SURVIVOR619
06-03-2012, 6:05 PM
Ramps
http://img.tapatalk.com/62b010c1-17cc-0589.jpg
http://img.tapatalk.com/62b010c1-17d9-8990.jpg


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SURVIVOR619
06-03-2012, 6:08 PM
Bolt and magazine...
http://img.tapatalk.com/62b010c1-17fe-638d.jpg

http://img.tapatalk.com/62b010c1-180d-8f34.jpg

http://img.tapatalk.com/62b010c1-1895-cb17.jpg

http://img.tapatalk.com/62b010c1-18a3-cc48.jpg


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Ruiner
06-03-2012, 6:09 PM
I'm going to say it's an issue with the magazines. This sometimes happens with the 20rd PMAGS when they are blocked. The follower gets bound and the rounds go up at a steep angle, causing the bolt to hit it at that exact spot. Try different mags if at all possible.

SURVIVOR619
06-03-2012, 6:09 PM
I had 4 of these magazines in rotation...


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SURVIVOR619
06-03-2012, 6:10 PM
What a bummer that magazines can be this easily finicky... Lame!


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ott1
06-03-2012, 6:18 PM
That's some dirty chamber.

Ruiner
06-03-2012, 6:21 PM
What a bummer that magazines can be this easily finicky... Lame!


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It's an unfortunate side effect of having to have magazines modified from their original specs. This issue tends to happen with modified 20rd PMAGS due to the follower design. Most people won't have issues with theirs, but it does happen. I have 2 that exhibit this very same behavior on at least 8 different rifles...

SURVIVOR619
06-03-2012, 6:22 PM
Just one day of shooting too...

Going to take my own thread partially off topic and say that my Frog Lube really gunked up my AR today...

Maybe the FL was getting sticky as it became dirtier..? Until now, I've been a huge FL fan, though used on firearms that did not require as much of the 'wet' factor as an AR... Bummed!


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SURVIVOR619
06-03-2012, 6:24 PM
It's an unfortunate side effect of having to have magazines modified from their original specs. This issue tends to happen with modified 20rd PMAGS due to the follower design. Most people won't have issues with theirs, but it does happen. I have 2 that exhibit this very same behavior on at least 8 different rifles...

Yeah and I thought their follower was nice in its purported anti tilt capabilities...


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Ruiner
06-03-2012, 6:25 PM
Yeah and I thought their follower was nice in its purported anti tilt capabilities...


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That's just it, the 20 rd PMAG doesn't have a true anti tilt follower unlike the 30rd one. :( One of the main reasons I use 10/30s.

SURVIVOR619
06-03-2012, 6:31 PM
Huh, did not know that... And the mags I pictured were 15 rounders cut down to 10... So no anti tilt there I guess..?


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Ruiner
06-03-2012, 6:40 PM
Huh, did not know that... And the mags I pictured were 15 rounders cut down to 10... So no anti tilt there I guess..?


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Yep. Magpul doesn't make a 15 rd specific pmag although some places sell them already blocked to 15. It's still the straight body 20rd pmag.

gunnerstuff
06-03-2012, 9:40 PM
I'd still go with short stroking. That is a bit of carbon build up in the bolt. Field strip it and check the gas rings on the bolt. Also check the gas port in the bolt carrier for any obstruction/build up.

paratroop
06-03-2012, 9:58 PM
Yeah before spending money on new mags, clean and lube, if problem persists, lube and lube. Some ars dont like certain types of ammo too. Then check mags.

SURVIVOR619
06-04-2012, 7:18 AM
Much appreciated gents.

I followed the classic lube advice for the BCG, however with FL... Time to find something else before returning to the range on Wed...


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luchador768
06-04-2012, 8:39 AM
What is your recipe for the reloads? How are you measuring your powder? I would bet that the problem is the round BEFORE the rounds pictured being under powered.

Sturnovik
06-04-2012, 8:51 AM
I had EXACTLY that issue. I was running a 10/20 Pmag, from riflegear. It was blocked and everything, but the bolt kept slipping over the rounds and when it didn't it was a jam that would do exactly that sent to my cartridges. I'd think yours was the same issue. I have other 10/20 mags, they run fine. Must have been a lemon from riflegear.

Garrman
06-04-2012, 9:16 AM
Had a buddy's carbine doing the exact same thing. We swapped the BCG from my carbine and the problem went away. Do you have access to another BCG you can try?

Worth a shot.

Good luck.

SURVIVOR619
06-04-2012, 9:42 AM
^ I do and will try using both a different BCG and different mags next trip out.. I was shooting alone yesterday so such items were not available..

I still think I'll try a different lube too...


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SURVIVOR619
06-04-2012, 9:44 AM
What is your recipe for the reloads? How are you measuring your powder? I would bet that the problem is the round BEFORE the rounds pictured being under powered.

The reloads I purchased and did not reload myself.. I shot at least 400 of those same rounds through my Saiga .223 without issue if that makes a difference..? 😳


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InkHammer
06-04-2012, 9:57 AM
^ I do and will try using both a different BCG and different mags next trip out.. I was shooting alone yesterday so such items were not available..

I still think I'll try a different lube too...


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Give slip 2000 EWL 30 a try! That is some great stuff and goes a long way. I use it on all my firearms and my AR is smooth as silk with it.

Panchira!
06-04-2012, 10:05 AM
Give slip 2000 ewl a try. I really like it in my ar's.

motorwerks
06-04-2012, 10:18 AM
With frog lube I dont have to run my AR's super wet. I get them hot in my toaster oven (I used to use my kitchen oven till I remembered I had the toaster oven in the garage) to warm them up to about 150 or so, then I take a finger and run some of the grease over the bearing surfaces (shiny spots) of the bolt, and bolt carrier, then once it all cools I wipe everything pretty much dry. Then just a couple of drops of the lube here and there to keep everything smooth.

duc748bip
06-04-2012, 10:29 AM
Could be the magazine follower, I never had good luck with Pmag that had been blocked or chopped. the follower push the front part of the cartrige to the line of the bolt but the rear of the cartrige is still below so the bolt slam right into the middle. Sometime when I push the follower down with my figer it feels like the rear of the follower is dragging on something i guess you can keep trying so it will just wear smooth. Because i don't think you want to put lube down the magazine body.

BMWguy206
06-04-2012, 10:37 AM
Like what others have said, try a different magazine. I had the same issues and turned out that my magazines were very dirty.

I wouldn't give up on the FL just yet. I've been using it on my AR with no issues.

May also want to try a H buffer if you're running a carbine gas tube.

Dave07997S
06-04-2012, 10:56 AM
Most of the time when I see rounds like the one you pictured its a magazine issue.

Dave

HPGunner
06-04-2012, 10:59 AM
I'm having similar issues, and its likely a magazine issue. The Mag springs probably needs a little breaking in. I have similar jams and it only happens on two of my aluminum metal body magazines (Circle K magazines) with Magpul followers and new springs. The rounds don't strip off the magazine as easily as some of my seasoned PMags. Also it only happens when I try to rapid fire. I would start with trying different magazines.

SURVIVOR619
06-04-2012, 12:35 PM
With frog lube I dont have to run my AR's super wet. I get them hot in my toaster oven (I used to use my kitchen oven till I remembered I had the toaster oven in the garage) to warm them up to about 150 or so, then I take a finger and run some of the grease over the bearing surfaces (shiny spots) of the bolt, and bolt carrier, then once it all cools I wipe everything pretty much dry. Then just a couple of drops of the lube here and there to keep everything smooth.

I use my wife's hair dryer to heat up my gun's parts and also use the "finger tool"... As mentioned, I've loved the FL for well over a year...


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SURVIVOR619
06-04-2012, 12:38 PM
Like what others have said, try a different magazine. I had the same issues and turned out that my magazines were very dirty.

I wouldn't give up on the FL just yet. I've been using it on my AR with no issues.

May also want to try a H buffer if you're running a carbine gas tube.

Are your wiping most of your FL off of the BCG? I think I may have left too much on it, applying the classic "oil" instructions... I did not consider the products, while having similar intentions, have some dissimilar properties..

Thanks


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motorwerks
06-06-2012, 5:42 PM
If you happen to be in the Sacramento area and can meet me someplace for shooting and troubleshooting I have a stack of magazines you are welcome to borrow. PM me I may never find this thread again.

SocomM4
06-06-2012, 8:31 PM
Tried hand cycling with dummies?

Or tried factory ammo?

jsipe007
06-06-2012, 9:54 PM
Are the locking lugs on the bolt in good shape? from the pic, the lug 2 below the extractor looks strange

loosewreck
06-06-2012, 10:37 PM
Yup, I bet it's the 10/20 Pmag, I have one that does the exact same thing. I believe there were threads on the same subject over on AR15.com and M4carbine.net, sorry I'm too lazy to search for them.

Midwest PX sells a 10/20 "Stubby" (http://midwestpx.com/product_info.php?cPath=15_69&products_id=455&osCsid=ikgqdm51v9g04tmrig17jopef0) that's cut down from a 30 Pmag, so it has the true double legged anti tilt follower.

SURVIVOR619
06-25-2012, 8:11 PM
After range visit this weekend I have to conclude it was a short stroking issue... One of my gas rings was bent from my rookie lubing error.. I replaced with McFarland single gas ring, used same dirty mags and shot 200 rounds of wolf wpa without a single feeding issue!

You AR docs are great and thanks for all the advice!!


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East Bay Cop
06-25-2012, 11:41 PM
Personally change mags if possible, try factory fresh ammo and lube it good and throw in an H buffer. May want to check headspacing as well. My Saiga eats everything too, my AR's not so much. Hope this helps.