Help with new Build Issue

[tappedandtagged]

I recently built an AR and am having issues. The rounds are not reliably strippingfrom the magazine and chambering. This is most prominent when trying to hamber a round by using the bolt release or manually. Didn't seem to matter how many rounds were in the magazine. Photos below. But first, build details:

Mega Arms forged lower
DSG Arms lower parts kit (including reciever extension, carbine buffer and spring)
BAD BCG (started with a brownells, but swapped it for a BAD when I thought the issue was bcg related)
Ballistic Advantage barrel
Magazines used are MOE Pmag, Troy, Lancer, Bushmaster factory and a variety of surplus/DRMO mags from the PD armory.

http://i820.photobucket.com/albums/zz121/zlwhite/IMG_0744_zpssvtznab7.jpg (http://s820.photobucket.com/user/zlwhite/media/IMG_0744_zpssvtznab7.jpg.html)

http://i820.photobucket.com/albums/zz121/zlwhite/IMG_0745_zpsuck1g0gf.jpg (http://s820.photobucket.com/user/zlwhite/media/IMG_0745_zpsuck1g0gf.jpg.html)

[Stickman]

Have you swapped out the buffer and spring?

[tappedandtagged]

Only with another carbine weight (from my factory-ish Windham). Same issue.

[UWone77]

Carrier moving too fast?

Sounds like you've swapped out the most common issues, the BCG, Magazine. I'd try a heavier buffer.

[FortTom]

Are you saying that with an unchambered round, you can pull back on the CH let it go, not "riding it down", and it won't strip and feed a round? Let me ask you a dumb question. Having tried everything UW has recommended, is it possible you've over loaded the mag by a round? I've seen that happen so many times, it's almost common. This is one of those "I wish I could see it' things. Also, are you shooting factory loaded ammo or hand loads? Good luck to you, I'd bet it's a simple issue, you've just got find it. One of those "DOH" things, like I do.[:D]

FT

[BoilerUp]

In my mind, there are two reasons why a round won't be picked up by the bolt:
1) short stroke - the bolt doesn't come back far enough to get behind the base of the next round
2) bolt over base - the round is just barely too low for the bolt to pick it up

#1 is a malfunction typically traced back to the gas system, including underpowered ammo, and is a very common issue
#2 is physical geometry of the weapon: magazine feed angle and the position of the magazine in the well as dictated by the magazine, machining of the lower receiver, and the magazine catch assembly. #2 is less common, but you'll be wasting your time chasing down gas system issues if it is the real culprit. It sounds like you've eliminated mags as the issue, so your next trick would be to swap out the magazine catch. I had one build where the combo of mag catch and lower just didn't reliably work. A different mag catch fixed the issue and that same mag catch worked just fine in a different lower. I seem to recall reading of a lower receiver where the machining for the mag catch was out of spec enough that there was no way to fix it short of replacing the lower receiver.

I hope that's helpful.

[tappedandtagged]

Carrier moving too fast?

Sounds like you've swapped out the most common issues, the BCG, Magazine. I'd try a heavier buffer.

Its not upon firing that it won't strip the round. Its when trying to chamber a round with an empty chamber.

[tappedandtagged]

Are you saying that with an unchambered round, you can pull back on the CH let it go, not "riding it down", and it won't strip and feed a round? Let me ask you a dumb question. Having tried everything UW has recommended, is it possible you've over loaded the mag by a round? I've seen that happen so many times, it's almost common. This is one of those "I wish I could see it' things. Also, are you shooting factory loaded ammo or hand loads? Good luck to you, I'd bet it's a simple issue, you've just got find it. One of those "DOH" things, like I do.[:D]

FT

Yes, you're understanding correctly. I'm not riding it down. Does this with factory and reloads.

Not an overloaded magazine. When testing, I would load each mag to 30, fire, while holding the bolt release to lock the bolt back upon firing. I would then hit the bolt release to chamber a new round, through the whole 30 rounds. Sometimes it would chamber, sometimes (~20%) it wouldn't. The number of rounds did not seem to make a difference.

[Tyrannosaur]

What type of magazine? Magpul or USGI metal perhaps? If they're the metal ones the trick is to leave two rounds out. When we could have 30 rounders in N.Y. all we could have were pre ban USGI mags. Could only load 28 rounds, never 30 for them to feed properly

[tappedandtagged]

What type of magazine? Magpul or USGI metal perhaps? If they're the metal ones the trick is to leave two rounds out. When we could have 30 rounders in N.Y. all we could have were pre ban USGI mags. Could only load 28 rounds, never 30 for them to feed properly

Magpul, USGI, metal Bushmaster, Lancer. Doesn't matter if downloaded to 28, 20 or even 15.

[Stone]

For starters your rifle looks way to dry. Lube the piss out of that thing, real important on a new rifle. Then while its unloaded cycle it 50-100 times to get the parts to mate up. It looks like its hanging up on the feed ramps of the barrel extension, do the bullets have deep gouges on them?

[FortTom]

For starters your rifle looks way to dry. Lube the piss out of that thing, real important on a new rifle. Then while its unloaded cycle it 50-100 times to get the parts to mate up. It looks like its hanging up on the feed ramps of the barrel extension, do the bullets have deep gouges on them?

Wow, I've been through this many times over. Always want to find the fiend to problem to be a simple one. Besides UW, Stickman and Stone, I would do what Stone recommend is looking at, gouges on ammo (my quepstion about factory ammo and hand loads). I'm not really a fan of lubing the shit out of it, kind of guy, unless your shooting old school phosphorous BCG's.

Hope you get it right. Lot's of guy's/gal's here to help you get it straightened out.

FT[:D]

[UWone77]

Its not upon firing that it won't strip the round. Its when trying to chamber a round with an empty chamber.

Ok, I'm following.


For starters your rifle looks way to dry. Lube the piss out of that thing, real important on a new rifle. Then while its unloaded cycle it 50-100 times to get the parts to mate up. It looks like its hanging up on the feed ramps of the barrel extension, do the bullets have deep gouges on them?

I agree. I can't tell you how many malfunctions are remedied with sufficient lube.

[Stone]

Not sure where it started but back in the day people were afraid to over lube so they end up under lubing. Maybe its a carry over from the military of days gone past. I run my rifles wet even more so on a new build.

[UWone77]

Not sure where it started but back in the day people were afraid to over lube so they end up under lubing. Maybe its a carry over from the military of days gone past. I run my rifles wet even more so on a new build.

Agreed. I usually lube all my parts before putting a rifle together. Then lube it again after I give the gun time to soak up the first lube.

[GOST]

Have you had a chance to try that upper on a different lower yet? Outta spec lower could have the BCG riding on either the hammer or mag. I've never had this issue but have read of similar experiences. One was an outta spec lower, another was an outta spec charging handle that was to tall. Hope you get it figured out.

[tappedandtagged]

Have you had a chance to try that upper on a different lower yet? Outta spec lower could have the BCG riding on either the hammer or mag. I've never had this issue but have read of similar experiences. One was an outta spec lower, another was an outta spec charging handle that was to tall. Hope you get it figured out.

I did try it with another upper. No issues. Likewise, the "problem " upper on another lower had no issues.

I need to get back to the range with all three of my rifles and swap parts around till something works.

Also, as for the lube, when freshly lubed (heavily) it would run a tad better (~15% failure rate vs ~20%). All stats approximate.

[GOST]

Looks like in your pics that a lug is showing some wear, maybe from rubbing the mag. I'm grasping at straws though, I'm a poor gunsmith.

[cjd3]

So I had a problem once with an out of spec upper. Does the carrier slide freely, with or without the bolt?

[tappedandtagged]

Looks like in your pics that a lug is showing some wear, maybe from rubbing the mag. I'm grasping at straws though, I'm a poor gunsmith.

I'll look at that closer. I haven't noticed any unusual wear.


So I had a problem once with an out of spec upper. Does the carrier slide freely, with or without the bolt?

Carrier slides/glides as it should without a loaded mag in place.

[tappedandtagged]

I dredged up some video from back when I was actually doing the testing of the build. The rifle has actually been in my gunsafe for quite some time. Deer season, and then crappie season got me sidetracked. Now that its summer and the fishing has laid off, I'm back to my summer hobby of guns.

Anyway, here's the videos I took (if they upload right). The Brownells BCG has already been sent back and replaced with a Battle Arms BCG. Although the videos only show the use of the factory metal mag, I tested all the mags I have at my disposal in the similar manner. I also tested it with downloaded mags (20 or less) to see if that would make things go better. They didn't. Now that I watched the video, I'm second guessing myself as to whether I swapped the buffer/springs out.

https://youtu.be/kbr7Q3to0UU

[tappedandtagged]

https://youtu.be/kbr7Q3to0UU

[tappedandtagged]

https://youtu.be/FDNMsMUXuHE

[tappedandtagged]

https://youtu.be/PSlcih5b-Fw

[tappedandtagged]

https://youtu.be/K5MplFoJa98

[tappedandtagged]

https://youtu.be/GSzzGcKre4U

[tappedandtagged]

https://youtu.be/g9XuJSSmllE

[tappedandtagged]

https://youtu.be/HFLIOiX7Sc0

[Stone]

Take some up close pics of the feed ramps and the bullets that are getting jammed up.

[mustangfreek]

How do the Feed ramps look?

Try a different bcg other then the brownells and bad ?

[Joelski]

Could be a tolerance issue, even with reliable, well regarded parts. I've had an enhanced bcg barely move in a billet upper, swapped it to a forged one and it hand cycles easily, even dry.

[Big_Tom]

The feed ramps would be my next thing to look at.

The upper and barrel extension may not line up as good as they should.

A little dremel time would fix that if so. Or just some good ol sand paper and a finger job.

Can you get a pic of the feed ramps with the upper detached from lower. Get them from the bottom where the mag would be.

[GOST]

Could be a tolerance issue, even with reliable, well regarded parts. I've had an enhanced bcg barely move in a billet upper, swapped it to a forged one and it hand cycles easily, even dry.
You're probably right, tolerance stacking is probably it.

[Joelski]

You're probably right, tolerance stacking is probably it.

Of in his case, matching, +/- a RCH.

[Stone]

On second thought I would just keep swapping parts at random until someday something happens. And whatever you do don't check the feed ramps. Take a few more videos as well, I thoroughly enjoyed them.[crazy]

[Stone]

The feed ramps would be my next thing to look at.

The upper and barrel extension may not line up as good as they should.

A little dremel time would fix that if so. Or just some good ol sand paper and a finger job.

Can you get a pic of the feed ramps with the upper detached from lower. Get them from the bottom where the mag would be.

Thanks Tom, seeing as how that was mentioned several times already maybe a third times a charm.

[UWone77]

Thanks Tom, seeing as how that was mentioned several times already maybe a third times a charm.

LOL.... and... a dremel to feed ramps?

NOOOOOOOOOOOOOOOOOOOOOOO!

[Stone]

LOL.... and... a dremel to feed ramps?

NOOOOOOOOOOOOOOOOOOOOOOO!

Sometimes I just want to stab myself in the eye with a sharp pencil....[bash]

[cjd3]

It's been recommended to me to use a Cratex polishing bit to blend the feed ramps with the barrel extension. Last ditch effort attempt. However, before you do that, have you swapped out the bolt catch? Could the carrier be riding it?

[tappedandtagged]

Sorry I've been away for a while. Work has me swamped.

Here's a pic of the feed ramps. They look OK to me, but I'm no armorer. Edit: I looked at several bullets that I've been chambering. They're buggered. So I guess the feed lips ain't so OK after all?

http://i820.photobucket.com/albums/zz121/zlwhite/IMG_0762_zpsgx3hhwzy.jpg (http://s820.photobucket.com/user/zlwhite/media/IMG_0762_zpsgx3hhwzy.jpg.html)

http://i820.photobucket.com/albums/zz121/zlwhite/IMG_0770_zps5cymlmjx.jpg (http://s820.photobucket.com/user/zlwhite/media/IMG_0770_zps5cymlmjx.jpg.html)

http://i820.photobucket.com/albums/zz121/zlwhite/IMG_0773_zpsh750y2cj.jpg (http://s820.photobucket.com/user/zlwhite/media/IMG_0773_zpsh750y2cj.jpg.html)

[Big_Tom]

Sometimes I just want to stab myself in the eye with a sharp pencil....[bash]


LOL.... and... a dremel to feed ramps?

NOOOOOOOOOOOOOOOOOOOOOOO!


Thanks Tom, seeing as how that was mentioned several times already maybe a third times a charm.



Yeah I know I just wanted to see if y'all actually read my post. And I skimmed the thread seeing if any thing wasn't mentioned. Guess I looked over the parts about checking feed ramps. And I just like throwing my 1cent around.

[tappedandtagged]

I swapped buffer, springs and charging habdle again, just to double check. No go still. After it failed to strip the round, Inpulled the charging handle back again and "hammered" the partially stripped round. It went forward, free of the mag lips, yet the bolt stayed hung up. I removed the mag, and the bolt went home, chambering a round. I was able to duplicate this several times with different mags.

http://i820.photobucket.com/albums/zz121/zlwhite/IMG_0768_zpsbaf4qzbf.jpg (http://s820.photobucket.com/user/zlwhite/media/IMG_0768_zpsbaf4qzbf.jpg.html)

[tappedandtagged]

Yeah I know I just wanted to see if y'all actually read my post. And I skimmed the thread seeing if any thing wasn't mentioned. Guess I looked over the parts about checking feed ramps. And I just like throwing my 1cent around.

I appreciate your 1 cent! Thanks for your input. Hopefully I'll be able to figure this put soon enough. Its been on the "back burner" for too long.

[Big_Tom]

I appreciate your 1 cent! Thanks for your input. Hopefully I'll be able to figure this put soon enough. Its been on the "back burner" for too long.

Anytime I know how much of a headache it can be when you can figure out the issue. I like to giving people a good chuckle a time and again. Lol

[Stone]

Yep, just having a little fun. It looks like there are a couple of burrs on the feed ramps from machining. If it is, it will dig into the copper jacket and stop the round dead in its tracks which is what it looks like from the original picture. I just resolved the same issue on one of my rifles at 3K rounds, it was bad and doing the same thing. I circled the area that looks suspect, any way to get a clearer shot? Are the bullets gouged real bad? Are you seeing excessive copper and brass shavings?
3703

[Stone]

Also, more times than not its a combination of issues. ETA: Just noticed the pics above of the gouged rounds, sure enough. I would pull the barrel and fix that up. Or if its new send it back for a replacement.

[Stone]

I put this together for folks that skim through threads and just land on the last page, enjoy...

This:
3704
Plus this:
3705
Equals this:
3706
[:D][BD]

[tappedandtagged]

Stone, thanks for the enhanced pics post!

For those with long memories, I sent a barrel back to Ballistic Advantage because it wouldn't hold 1 MOA. They replaced that barrel with an upgraded one (Hanson) and when they mailed everything back, they included the old barrel as well. I used that "free" barrel to build this iron sights only rifle. Of course it has no warranty now, so I'll be pulling the barrel myself if I see any burrs there. I'm thinking it may just be glare from my crappy iPhone pics in bad lighting.

I'll try to get my wife to take some better pics with her nicer camera, or better yet, one of the crime scene techs at work! One of them has been bugging me for a new camera, so maybe he can "earn" it by being my photographer. Actually, he does have an old camera and is in need of a new one, he just hasn't gotten me the price quotes I asked him to get me back in January.

[tappedandtagged]

Alright! I should be in bed, but I had to get up and pull the rifle out if the safe again. Sure enouh, those are burrs that Stone pointed out. Thanks Stone!!

I'm guessing just pull the barrel and gently remove the burrs with a needle file?

[SINNER]

Looks like the issue is at the bottom of the feed ramps at the interface with the upper. I'd touch it up with a needle file since it's a jacked up barrel anyway.

Damn good chance the tolerance stacking was less with the other upper and although it was functioning it was still damaging the bullets and causing your inaccuracy issues.

[Big_Tom]

I put this together for folks that skim through threads and just land on the last page, enjoy...

[:D][BD]

I'm usually I pretty damn good skimmer. I try not to be that one guy. Lol but we all know there is always that one guy. [BD]

[mustangfreek]

but we all know there is always that one guy. [BD]

...we do......[:D]

Ok so had to go back and watch the video, the rounds are getting hung up so bad it's stopping in this lower?

Does it do the same in a different lower?

I'd try Grabning a known good rifle check out the ramps/how it looks and then just swap out that bcg into this upper and see what it does, then the lower?

I mean chambering a round is gonna scratch it up some.. But something isn't kosher there.keep us posted

[Stone]

Alright! I should be in bed, but I had to get up and pull the rifle out if the safe again. Sure enouh, those are burrs that Stone pointed out. Thanks Stone!!

I'm guessing just pull the barrel and gently remove the burrs with a needle file?

Yep, that's what I did. Take your time with it and try not to let the steel shavings fall down the bore. Give it a deep clean afterwards and use some Flitz and a polishing wheel. Like the other guys mentioned there may be another issue or two as well. So once you solve this one keep your expectations in check. When you put it back together lube it up real good, initially, more is better...

@Big Tom, all in good fun buddy! [:D]

[tappedandtagged]

I just pulled the barrel, filed a small bit with a needle file, then sanded with fine grit sandpaper and put her back together.

Upon hand cycling, I had no issues out of any mags (Troy, Pmag, Lancer, factory metal). I then took the four mags to the range and test fired the rifle. For the first 10-15 I held the bolt lock back down and chambered each round by pressing the bolt release. I had ONE failure to fully chamber. The was stripped from the mag and fed into the chamber, but the bolt did not fully close. This was at round count ~100 on a completely dry supressed gun. I may still have a small but of excessive friction in the ramp area, but it should smooth out with shooting and lube.

Thanks for the help!

[Stone]

Glad you got her dialed in!