Stripped Round Will not go into Battery

[warthog984]

Hello.....This issue is driving me nuts.  I just built a new AR 308 and i cannot get the bullets to feed into the chamber when I charge the handle.  I have tried three different ammo types.  AE 150gr., Federal 168gr., Prvi 168gr.  All of them strip from the magazine but hang-up about 3/4 into the chamber.  It almost appears that the angle is too steep when being fed into the chamber.  On the one side of the brass you can see rub marks when I pull the brass out.  Also, the bot pushes so hard on the brass while it is in the chamber that I have to pull real hard on the charging handle to get it out.  The weird thing is that it does not get to the point where the bolt extractor grips the bullet case.  The bolt lugs are only touching the case.

 

I have verified that the bolt does go back far enough into the buffer tube.  The bolt catch works when the mag i empty.  I tried using PMAG Gen 2 and Gen 3 mags.  Parts are listed as the following:

 

Aero Precision Upper and Lower combo

Mega 16" barrel

Rainier Raptor charging handle

Magpul UBR

DPMS carbine buffer

DPMS Carbine buffer spring

DPMS BCG

 

I did head space the barrel and bolt and it passed.  I can put a live round in the chamber and the bolt closes and extracts when I pull the charging handle.  If I lay the gun down on its side resting on my table and pull and release the handle slowly, I can get it to feed on occasion.

 

I broke one rule that I have never done in the past.  I bought a product that just came to market (Aero Upper and Lower in 308).  I have had really good luck in the past with Aero Ar15 lowers.  I figured they are good to go.  Not sure if this problem is related to the lower or not.  The M4 feed ramp cut outs look like poop on the upper.  I dont think this is the problem since the brass will feed 3/4 into the chamber.  I dont know if the m4 feed ramps were cut at the wrong angle on the barrel extension.  Seems to be at an odd angle.  This is my first AR 308 build.  I have build about 20 AR 15s with no issues like this.

 

I have lubed the hell out of the bolt carrier.  I used Brownells Action Lube.  Very slick.I am running out of ideas.  

[Rsquared]

First. Welcome to the forum warthog. 2nd. Did you buy the BCG as a complete unit? 3rd. Some pics would help so all of us could get a look at it.

 

It seems like a lot of DPMS patterned rifles have tight chambers. But that shouldn't stop the action by hand. At least you wouldn't think (things are moving a lot slower).

 

But just to be sure. You're having feeding and ejection problems?

 

We have to start somewhere.

[edgecrusher]

First issue I spotted: wrong buffer/ spring combo, and possibly receiver extension (buffer tube)

You said you were using the UBR but had carbine parts. That's a no go. You need to be using a rifle buffer and spring combo as well as an A1/A2 extension. Let's start there, and try again before anything else.

Btw, I would trust the aero stuff, for now I believe your parts are just wrong.

[Rsquared]

Negative there Edge. I use carbine springs and buffers (heavybuffers) in my UBR setup. They work fine (granted I'm Armalite, not DPMS). And it comes with the proper extension.

[edgecrusher]

Hmmm, my bad.

Then let's go with tight chamber?

[warthog984]

First issue I spotted: wrong buffer/ spring combo, and possibly receiver extension (buffer tube)

You said you were using the UBR but had carbine parts. That's a no go. You need to be using a rifle buffer and spring combo as well as an A1/A2 extension. Let's start there, and try again before anything else.

Btw, I would trust the aero stuff, for now I believe your parts are just wrong.

 

Magpul UBR uses AR15 carbine length buffer tube.  I have a DPMS 308 Carbine buffer and spring from Midway USA.  What I notice is when I hand cycle the round, it pops out of the magazine feed lips and goes at an awkward angle.  The rounds seem to bind on top of the chamber.  I have no problem with extracting and ejecting the ammo if i stick it in the chamber and close the bolt.  The bolt carrier group was bought as a complete unit from Midway USA also.

[Rsquared]

When you hand cycle it? Are you pulling back and letting it "slap" into battery? Just wondering.

I'm scratching my head now.

[warthog984]

Hmmm, my bad.

Then let's go with tight chamber?

My thought was tight chamber.  The rounds do drop in the chamber easy by hand, but it fits like a glove.  I dont know if it only a thousandth of an inch hanging it up.  I put some light grease in the chamber hoping it would allow the round to slide by.  Anyone else have a Mega barrel care to comment?

[warthog984]

When you hand cycle it? Are you pulling back and letting it "slap" into battery? Just wondering.

I'm scratching my head now.

Yes.  I have tried letting slam forward as hard as possible.  I can get it to feed if I set it on its side and place it on my chair and cycle the handle real slow.  If I go real slow I can watch the round pop out of the magazine feed lips and tilt the rear of the case up and then the round kind of self centers itself back into the chamber.  I would have thought the round would funnel better into the chamber.

[warthog984]

I just tried PMC 147gr and Federal 7.62 OTM 168gr.  Same results.  I am going to try the local SG store to see if they have any DPMS steel magazines.  I am also go to take the gun out and manual load a round in the chamber and fire it to see if the results are the same.

[Toolndie7]

Warthog, Is the chamber nicely polished?

 

A friend of mine just did a build and he used a mega 16" barrel, awesome barrel with no issues but I did notice that his chamber was not polished, he had some cycling issues at first but once it was broken it he says its fine.  I don't know maybe its just enough drag to give you a hard time?

[Robocop1051]

I'm wondering if magazine seating is correct??

Take out your mag catch and see if your magazine can seat deeper.

Are you trying to load from a full magazine? Or are you loading 1 or 2 at a time?

[warthog984]

Warthog, Is the chamber nicely polished?

 

A friend of mine just did a build and he used a mega 16" barrel, awesome barrel with no issues but I did notice that his chamber was not polished, he had some cycling issues at first but once it was broken it he says its fine.  I don't know maybe its just enough drag to give you a hard time?

 

 

I'm wondering if magazine seating is correct??

Take out your mag catch and see if your magazine can seat deeper.

Are you trying to load from a full magazine? Or are you loading 1 or 2 at a time?

 

Toolndie7  the entire barrel is melonite coated.  The chamber is not polished.  I was thinking of calling Mega on Monday to ask them if there is any way to polish it.  I hand cycled this gun over hundred times.  I just got back from the range.  I manually put a round in the chamber and fired it.  No issues extracting a single round.  I then put a round in the chamber and two in the magazine.  After the fired round ejected, the new round would jam in the chamber 3/4 of the way.  Same issue as manually cycled from the magazine.  I dont know if this issue will get better through breaking in.  My understanding is melonite is some tough stuff.

 

Robocop 1051 I did exactly what you mentioned with the mag catch yesterday and had the same issues.  I have an Armalite AR10A mag catch.  I was wondering if that was the issue, but it does not appear to be related.  

[Robocop1051]

I'm using the AR10A mag catch as well. I doubt that's the issue. It's a better part than the other options available.

I say you invest $5.00 in a chamber brush and some 000 steel wool. Chuck the brush into a rotary tool (a drill works, but a dremmel works better) and polish up the chamber. Then work on the feed ramp.

You might have to check out some steel magazines. I know at least one guy here has a rifle that refuses to uses Magpul mags, but runs fine on steel DPMS LR308 mags.

[survivalshop]

  Try a steel magazine  or two , even if you have to barrow one . Yes , I have a CMMG lower that will only work with metal mags , LR PMags will malfunction just as you describe as was mentioned above . Also Make sure your barrel extension feed ramps match up with the M4 feed ramps on the lower receiver , because if they don't & theres any bump or lip , it will produce the same FTF.

 Of all the ammo that should cycle in these rifles is mil sec ball ammo. Usually , feeding problems are associated with the Magazine in some way.

[warthog984]

  Try a steel magazine  or two , even if you have to barrow one . Yes , I have a CMMG lower that will only work with metal mags , LR PMags will malfunction just as you describe as was mentioned above . Also Make sure your barrel extension feed ramps match up with the M4 feed ramps on the lower receiver , because if they don't & theres any bump or lip , it will produce the same FTF.

 Of all the ammo that should cycle in these rifles is mil sec ball ammo. Usually , feeding problems are associated with the Magazine in some way.

 

Thanks for your input.  I was hoping to hear about a similar issue to gauge how to fix it.  Are DPMS the best steel magazines?  What about AR Stoner?  I dont think I would bother with ProMag.  Any other steel magazines that I have not listed? The M4 cut outs are are not that great on the Aero upper receiver.  It looks like the rounds are hitting on the middle of the  barrel feed ramps, so I was not to concerned with the poor cut outs on the receiver. If I saw copper marks on the upper receiver cut outs, I would be concerned.  I was thinking about grinding the receiver to match, but I did not want bare aluminum.  

[blue109]

someone on here is selling KAC mags. id have to assume they are the best based on the obscene price tag.

[edgecrusher]

I have some c-products mags that work fine, if you can't find another solution, let us know

[guruofhotrod]

I bought some stainless 10 round mags from these guys:  http://www.ammosc.com/

 

Haven't used em yet - still wrapping up my rifle - and before anyone asks I didn't buy the pink ones!

 

Lanbo's Armory in Texas has them at discounted prices

Edited August 3, 2014 by guruofhotrod

[Matt.Cross]

Have you tried pushing the bottom of the mag towards the muzzle and cycling the action? Your feed ramps on your barrel extension are what my money is on right now. Try pushing and holding the bottom of the mag forward (towards muzzle) and cycle the bolt, releasing the charging handle at the extreme rear of it's travel. If it loads rounds correctly in that manner, see if it will cycle correctly being fired in that manner. There is a possibility of your mag well angle being incorrect, but it's so slight that it's almost impossible.

[warthog984]

Just tried the holding the magazine forward and cycling the handle.  No luck.  i also tried it while holding the magazine towards the stock.  No luck either.  I ordered 4 magazines from Midway USA last night.  Two DPMS 20 rnd, and two AR Stoner (ASC).   Hope it does the trick.  I looked for C-Products, but Aim is the only place that has them in stock.  They only have one in stock and want $11 to ship.  The reviews for C Products are horrible on Palmetto States website.  I wonder if they discontinued the 308 magazine.

[edgecrusher]

They had two iterations, through two ownerships. I have gen 1 and have zero issues with the five I've used (several... still in wrappers) I think survivalshop has one I sent him a while back for testing purposes and also had success

I know the second gen are crap in 308 and 5.56.

I hope this solves it for you, it's an easy fix to just get certain mags

[survivalshop]

  All my older C-products 308 mags work fine & it was more than one mag ., I think I bought ten from someone  <thumbsup>.  I can't see your feed ramps being a problem , but how the magazine feeds the round & at what angle .

   I found through measurements that it doesn't take a Magazine's seating height ( or lack of it ) to make them cause malfunctions , we are only talking about a few thousands of an inch to cause problems . Because that is what I found with the CMMG lower & the PMags . Now in CMMGs defense , there lower Receiver was designed & purchased long before a LR PMag was made , maybe why the steel mags work . Tolerance stacking , I even tried two different DPMS upper receivers on the CMMG lower with the same results .

 

[Robocop1051]

@Warthog984

Fwiw, you'll get a lot of info from a lot of us... but we all go to SurvivalShop when we need advice. I really think he's Eugene Stoner, masquerading on our site as the wise old man on the mountain. Most of our experience is just regurgitated info he already imparted on us when we had a similar issue. Honestly, if he said changing my front sight post would improve my weapon cycling, I'd swap that bitch out immediately.

[j.peace]

My thought was tight chamber. The rounds do drop in the chamber easy by hand, but it fits like a glove. I dont know if it only a thousandth of an inch hanging it up. I put some light grease in the chamber hoping it would allow the round to slide by. Anyone else have a Mega barrel care to comment?

I've got the mega 18" chamber was tight to begin with . I chambered about 5 different kinds. All were tight. I lapped the chamber before firing with bore brite. Headspaced fine before and after lapping. Everything runs fine. Sub 1 moa at 100 just like advertised.