New build doesn't run!

[ben b.]

Gas ring alignment is almost certainly not an issue, ever. How easily does the BCG go in & out of battery with finger pressure (not Charge handle and/or buffer spring)?

I would work at figuring out on your own, before handing it off, you learn a lot about the operating system.

[openclassterror]

My son used that Independence stuff in the match last Saturday. In a rifle that has been quite dependable he had about 15 short strokes over 3 stages with a total round count of about 50-60. After the match I took his rifle up to an empty bay and dumped 2 partial mags of Federal 55gr FMJs from my match leftovers (about 30-35 rds total) with ZERO malfs. Might try some good ammo. I was not impressed with that stuff.

[Mike_M]

Mike find someone in your area and have them look at the gun. We can set here all day and guess wants wrong with it are you can get fine someone that can lay hands on and get it fixed. just my 2cents.

02 - yeah, I'll do just what you suggest if it comes to that. There's a few places I can take it.

Gas ring alignment is almost certainly not an issue, ever. How easily does the BCG go in & out of battery with finger pressure (not Charge handle and/or buffer spring)?

I would work at figuring out on your own, before handing it off, you learn a lot about the operating system.

Ben - I'm at work and can't say for certain, but I'd say it doesn't take a TON of pressure to get the BCG into battery if I just manipulate it with my finger. Maybe 10 lbs of pressure does it (like a heavy trigger pull)?

And yeah, I'm learning lots, so thanks!

My son used that Independence stuff in the match last Saturday. In a rifle that has been quite dependable he had about 15 short strokes over 3 stages with a total round count of about 50-60. After the match I took his rifle up to an empty bay and dumped 2 partial mags of Federal 55gr FMJs from my match leftovers (about 30-35 rds total) with ZERO malfs. Might try some good ammo. I was not impressed with that stuff.

OCT - that's good to know. Thanks for the feedback. I think I'll just use that Federal stuff I have next test run.

So what do you guys think? Pull my barrel off, re-torque the nut and just pay extra attention to how the gas system lines up as I put it all back together again? I mean I basically have the upper apart except for the barrel anyway, may as well pull it off and redo everything. Also, do you guys use antiseize on the barrel nut? I did not do that. I cleaned it with brake cleaner and installed it dry, but since then I've seen several posts on BE that says to use a moly grease or antiseize. So maybe I'll try again...

What lube on the Bolt have you guys had good luck with? Bearing grease?

-Mike

Edited December 27, 2013 by Mike_M

[Moltke]

Your problem could be a variety of things - gas port, chamber dimensions, gas block, gas tube, bolt, and the rest of the stuff listed here. I'd guess that its not the buffer or receiver extension based on what you described.

Lubricate your bolt and carrier heavily with a gun oil, not grease - Militec, CLP, FIRECLEAN, are good examples.

If you don't have any matches for a week or two, I'd recommend breaking it down and looking for anything suspect such as damage or wear, and get some good factory ammo.

[ben b.]

So what do you guys think? Pull my barrel off, re-torque the nut and just pay extra attention to how the gas system lines up as I put it all back together again? I mean I basically have the upper apart except for the barrel anyway, may as well pull it off and redo everything. Also, do you guys use antiseize on the barrel nut? I did not do that. I cleaned it with brake cleaner and installed it dry, but since then I've seen several posts on BE that says to use a moly grease or antiseize. So maybe I'll try again...

What lube on the Bolt have you guys had good luck with? Bearing grease?

-Mike

Plenty of folks use Mobil-1 synthetic for the BCG, both serious gun-gamers and pro-soldier types. I would not grease the BCG. Maybe with SlideGlide, but I haven't tried it on BCG.

i would definitely grease the receiver threads & barrel nut threads, a tube of black moly grease works & lasts forever, lithium grease works, anti-seize works, bearing grease probably works fine. It should NOT be dry, especially when you start torquing it. 10#s of pressure seems like a lot to me, but if you can move BCG in n out of battery with just fingers it is likely fine.

Since you tried 2 ammo types with similar outcome, I would factor out ammo for now.

I would take apart & reassemble, checking gas port alignment and ensuring a free gas tube/gas key interface. Did you ensure that the barrel was all the way in, so that ramps on barrel extension mates with ramps on receiver? With the BCG removed, do loaded rounds plop easily in & out of chamber?

Edited December 27, 2013 by ben b.

[Alaskapopo]

If the key is not binding on the gas tube, is it tight and properly staked? Is the key clear (run a pipe cleaner through it). Does the bolt rotate freely bak and forth within the carrier? Are teh gas rings properly aligned on the bolt? And I know you said it was passing air, but are you SURE the tube is free and clear? And, this one is almost too obvious to mention, have you tired some known GOOD strong ammo?

Key is tight and staked. Air compressor on the gas key positively "pops" the bolt forward. I did make sure the gas rings weren't all lined up forming a leak there. As for ammo - I used Independence 5.56. Is that stuff crap? Well, I think I also used about 5 rounds of the XM193 Federal stuff too I think (brown box). These aren't reloads. Is it possible the barrel is mismarked and it's actually a .223 barrel? What would the expected result of firing 5.56 in a .223 barrel be?

PS - I have NOT run a pipe cleaner through the gas key, but I sure can try that tonight...

Just a quick note the gas rings being alinged is not an issue its a myth. Reason being is the rings are collasped when the bolt is pushed inside the bolt carrier closing any gap. An AR will run on just one gas right.

I had some issues with a Krieger barrel build and it turned out I needed small base dies. But I assume your using factory ammo.

[02Fatboy]

Is the gas tube pinned to the gas block? if not this will cause big problems. I think went you find someone who knows about AR's they can show you what the problem is on the AR. And I know how much you want to fix it yourself, about sometimes you can over look the easy stuff.

[openclassterror]

I use Shooters Choice red gun grease on the cam pin ONLY, and CLP on the rest of the BCG. I have noticed a HUGE reduction on cam pin wear from the cam slot, and the grease stays put and doesn't migrate onto the carrier like others I have tried. I have noticed across the board that when it is cold at our matches (under 30 deg), MOST gun oils get sluggish and I see a LOT of short strokes/ double feeds as an RO. CLP applied the morning of the match seems to stay thin. Hoppes seems the worst, Outers a close second for going goopy when it is cold. In 20 years of shooting I never saw this until I started shooting 3gun, because I never shot an AR when the weather sucked!

Tom

[Mike_M]

After re-aligning the gas block, I pulled the bolt out of the BCG to see how well the gas key lines up with the gas tube. The bolt carrier slides all the way forward with no resistance at all. I put Mobil-1 on the bolt and the carrier rails and checked to see how difficult it is to put the gun into battery with just finger pressure. It goes into battery easily. When I thought it had 10 lbs of pressure before I didn't realize that I was ALSO trying to push the charging handle latch. So without the charging handle in, the bolt goes into battery with maybe 5 lbs of pressure (easy). So I put the hand guard back on and headed to the range.

The good news is that I should about 12 rounds with no failures! I did note that the bolt didn't lock back on an empty magazine. I also noticed my ejection was still pretty weak. Then I started having a failure where the round was getting jammed at a very steep angle above the barrel and the bolt was denting in the side of the unfired round. So after about 2 or 3 of those issues I decided to pack up again.

This time at the range I was shooting Federal xm193s or whatever they are. I think I started having the jams on PMC.

Given the weak ejection still, I decided to drop it off at the local AR gun shop. I hate to do that, but I think I've tried everything you guys suggested. And I will say today it shot WAY better than it did, but it's still weak...

I'll let you know if they find anything...

Thanks a ton guys!

-Mike

PS - the guy shooting to the right of me told me that he thought he was going to get showered with brass so he stepped back when I started shooting. After watching a few rounds he decided to sit back down again and shoot. He said my brass was barely clearing the edge of the bench so he figured he was safe!

[ac4wordplay]

...Then I started having a failure where the round was getting jammed at a very steep angle above the barrel and the bolt was denting in the side of the unfired round. ...

Something fitting that description occurred to me. I traced it to the magazine - weak feed lips.

[ben b.]

Sounds like weak action, maybe a gas/unlocking problem, to me. BCG isn't going all the way rearward.

[ac4wordplay]

Sounds like weak action, maybe a gas/unlocking problem, to me. BCG isn't going all the way rearward.

Yes. I wondered if he might be unfortunate enough to have more than one issue - further complicating diagnosis.

[Mike_M]

Ah crap. I've had a gas problem my whole life and now my rifle has it!

[Mike_M]

My mags are Magpul PMAG 30 Gen M2. I have 2 of them and have been trying to make sure I'm getting the same issues with both mags. The other thing is, I'm still not getting the bolt to lock back on an empty mag so I think I have to agree that I'm not getting my bcg to come all the way back...

Edited December 29, 2013 by Mike_M

[Mike_M]

Just to update you guys - I just got off the phone with the gun shop. They tried my upper on a different lower and it ran fine. So they suspect my Vltor Emod A5 stock kit is the problem. Since I was kind of leaning that way as well, I spoke with Vltor yesterday and asked them if my issues sound familiar and the girl I talked to said that it's possible I need a different weight buffer. The A5 stock kit uses proprietary buffers, but the buffer that my stock came with was a 5.3oz buffer and she said I might want to drop down to their "H1" at 4.56 oz. So based on that, the gun shop was going to take some weight out of my buffer and see if it would run with a lighter buffer. I'm waiting for a call back. If it doesn't run, they said I could buy a standard length buffer tube and run a standard buffer in there, but still use my Emod stock. So that's one thing I may do.

But one thing the girl from Vltor told me has me a bit puzzled and I wanted to see what you guys think. She asked if my bolt was coated (it is and Nickel Boron coated BCG from Raineir Arms). She said that they're seeing a LOT of issues with coated BCG that need a few hundred rounds of break in before they run reliably. Something about very tight tolerances and then the coating seems to take them out of spec (my paraphrasing)... Anyway, was curious what the experts say about NiB coatings on BCGs...

-Mike

[ben b.]

To coat they need to be machined undersized and then coated up to spec. Last I heard only a few mfgs were actually doing that.

[openclassterror]

I am sure this is a stupid question, but are you SURE the gas key is tight? I had an experience this week for the first time ever where a gas key with good, heavy staking had loose screws. It was cycling weakly just like you described, and the customer was pulling his hair out. Just for the hell of it, I put an allen wrench on the gas key screws, and both were about 1/2 turn loose UNDER the staking! Seems like these new coated carriers don't hold torque like a parkerized one does. They are almost TOO slick, and some of the companies coating the carriers aren't staking the gas keys at all. I removed the key, loctited, torqued, and re-staked. Problem solved, back to full cycling. Just something to check.

[Mike_M]

Ok, so I put an allen wrench on the gas key and I do think I turned them somewhere between 1/8 and 1/4 turn each. Is that enough to make the difference between a gun not running and one that works?! It's not like the key felt loose...

Ok, so another session at the range last night and gun still doesn't run. I met a couple of really nice guys there who helped me out by swapping parts on my non-functioning gun to his gun that works fine. The only problem is, we tried so many things it's tough to rememeber the exact results of each. We shot my upper on his lower. We shot his upper on my lower. We shot his BCG in my upper. And I think what we narrowed it down to was that my BCG did it's normal short stroking in my gun, but when I run his BCG my gun ran flawlessly (bolt locked back on empty magazine, ejection seemed "right"). The only thing we noticed was that my BCG had some funny machining just past the end of the gas key. Still, the more I think about that, I don't see how that can be the issue... I guess the only thing I didn't do (and should have) was put a caliper on his BCG in various places compared to mine.

One other thing the guy noted was that he's heard of issues with the Magpul BAD lever causing problems. So I think I'll remove that just to eliminate another variable.

Anyway, here's a few pics.

[lc2hl]

Was his bolt an ar15 BCG? The reason I ask is that the bottom of the bolt in the pics is full. The ar15 BCG is shorter. I have a friend who had that exact issue with his. Gun runs great with an ar15 BCG, but has issues with mil spec weight BCG. The Simple fix was to change the BCG. Gun has run for quite some time without an issue after the change.

I would trace it to buffer / spring / stock combo, affected by weight from your description above. The MilSpec should work just fine if everything else in recoil / gas systems are in spec.

[Mike_M]

I'm a little confused. Ok, so I HAVE seen a few different "kinds" of BCGs available and I don't understand the differences. I see you can get a Full Auto M-16 BCG, and AR15 BCG, and then even a "match" BCG. So you can tell by looking at my bolt that mine is NOT an AR15 bolt? I actually had that question as I was re-looking at BCGs. Which one do I WANT? Do I want to skip the M16 full auto and match grade bolts and stick with AR15 specific ones? Any recommendations?

Thanks,

-Mike

PS - no, I have no idea what "kind" of bolt his was. It was a BCM and it was black. :-)

Edited January 10, 2014 by Mike_M

[lc2hl]

Here you go. Jump to 2 minutes, you will see the differences pretty quick.

https://www.youtube.com/watch?v=4X_D6UH3dLM

[Mike_M]

Ah, so then I have an M16 bolt. Thanks for the video, that answered a lot for me! So explain this to me, if it's the weight of the BCG that's the real difference between an M16 not running and an AR15 bcg running, then wouldn't I get the same effect if I dropped the weight of my buffer? So right now I'm running a Spikes T-2. Maybe I should just go get a lighter buffer to offset the extra weight of the bolt. Thoughts? I mean it just seems way cheaper for me to replace my buffer than my BCG, right?! Or is there more to it I just don't understand (VERY possible!).

I'm learning a ton here. Thanks a million!

-Mike

[lc2hl]

I run a JP spring / BRO Carbine Buffer and an ar15 bolt with some lightening. The spring can make a huge difference, more than most people think. You are correct, the buffer would be cheaper. You may also want to consider removing a weight in the one you have now and see if that solves the issue.

ReReading your earlier post, I would make sure the gas key is tight and properly staked again if you moved the bolts.

[bladewurk]

I'd return the BCG if Rainier will take it back.

[Mike_M]

I'd return the BCG if Rainier will take it back.

As in get something different, or just get them to replace this one (for another one just like it)??? I did call them this morning and they would absolutely send me a replacement if I send this one back, but I didn't ask if I could just get a refund.