Failure to feed on new build

[madmike66]

Took my new build/first Grendel to the range today to test fire and zero.

I put 50 rounds through it, but had to manually load a round from the magazine every single time, due to the BCG not stripping a round from the mag.

50 shots, not one semi-auto feed.

Observations:

1) The bolt locked back on an EMPTY mag every time.
2) If I hit the bot release it would not feed a round...I would have to pull all the way back on the CH and release to load a round.
3) 40% to 50% of the time when I did this, I would have to mash the forward assist to get it to fully seat.
4) When it would fully seat on its own, half those times it slammed right into battery, the other half it certainly felt/looked a little sluggish.
5) I am using a Spikes T2 buffer. I reached in my range bag to swap it out for a standard weight carbine buffer, and like a moron aparrently I had put it away, so testing that I was SOL.
6) Using a 10 round E-lander magazine. Also moronic, I did not bring my 17 round E-lander to test if it was the magazine.
7) Twice the rifle did this, when the bolt dented the casing because it half-fed:


Build details:

• Northtech Defense billet receiver set
  
• AA 16" Lite barrel w/WCI pepper pot brake
  
• Seekins SP3R V3 12" rail
  
• Voodoo Innovations lifecoat integral bolt carrier with AA bolt
  
• DPMS lower parts kit with Seekins enhanced parts and Strike Industries takedown pins
  
• Magpul STR stock and Ergo Tactical Deluxe grip
  
• Geissele SD-E trigger
  
• Vortex Viper HS 6-24x50 scope, Bobro Vortex cantilever QD mount.
  

So what do we think the culprit is:

Is it a magazine problem?

Is it the buffer, i.e. too heavy?

Is it the buffer spring?

It seems to me that 2 things are happening...1) the BCG isn't travelling rearward far enough to catch the back of a round and strip it and 2) it's travelling too slow to slam home with enough authority.

What say the horde?

[Younger]

Have you lubed the rifle and BCG? A new rifle needs lots of lube. Cleaning and lightly lubing the insides of the magazine will help feeding.
The AA barrel doesn't require a heavy buffer nor should it need one. Check gas block alignment.

[madmike66]

Have you lubed the rifle and BCG? A new rifle needs lots of lube. Cleaning and lightly lubing the insides of the magazine will help feeding.
The AA barrel doesn't require a heavy buffer nor should it need one. Check gas block alignment.

I lubed it up after I started having the problem, and while it seemed to help a tad with the bcg being sluggish, it still did not strip. I normally don't run rifles really wet, but when I got it home I cleaned it and lubed it liberally.

I'm def thinking I need to swap out the buffer for a standard weight one and try that.

I did disassemble and clean and lube the magazine prior to use, per the instructions on the package it came in. I don't think it's a matter of the magazine follower and spring being able to move freely.

I'll check the gas black alignment if the buffer swap doesn't fix my issue. I was reeeeeeeeally careful installing it.

[rabiddawg]

Is it possible you warped the upper receiver when you assembled and torqued the barrel nut?

Does the bcg slide freely in the upper without being attached to the lower? I don't really know what symptoms a warped upper presents rather just trying to eliminate that area.

One of mine had a leaking gas block. It would lock back on the mag but not cycle far enough back to lock on the bolt catch. This caused my cases to get bent just like your pick shows.

I'm no ar doctor but in my mind it's under gassed thus the buffer spring isn't getting loaded enough leading you to believe it is slow.

[VASCAR2]

The E-Lander mags have very strong springs when new. I suggest you load them to capacity and let them set loaded a couple of weeks or till your next test session. I always try to run a new build's BCG wet with lube (I normally use Breakfree CLP) but any brand lube should help. With the new build wearing in a lighter carbine buffer might allow the BCG to travel farther to the rear, looks like your rifle is short stroking. Upward pressure from a loaded mag pushing up against the bottom of the bolt carrier adds drag. You can try loading two rounds in the mag, charging the weapon. If the weapon cycles and feeds the top round then try loading three rounds. If both rounds feed then you know the rifle is capable of feeding from both sides of the magazine. Extra rounds loaded into the mag might be putting enough drag on the bottom of the carrier to inhibit full travel.

[Drillboss]

One of mine had a leaking gas block. It would lock back on the mag but not cycle far enough back to lock on the bolt catch. This caused my cases to get bent just like your pick shows.

This looks like the problem. See if the bolt is locking back on the magazine carrier and not getting all the way back to the bolt catch. I had this happen with some lighter reloads on a new build. I had my gas block partially covering the port.

[37L1]

Try a mag other than the Elanders?

[madmike66]

OK, update. Just got back from the range, and tried a few things.

First, lubed it silly.

Second, swapped out for standard weight buffer.

Third, brought the 17 round e-lander as well.

This time, the rifle fed fine. I would load 2 to 5 rounds, and feeding wasn't an issue. Releasing the CH felt sluggish one time, otherwise the BCG seated with no issues. Didn't have to touch the forward assist once.

However, now it doesn't fully lock to the rear on an empty mag. I tried both magazines, and aside from the very first time I shot it to empty, it locked halfway. See pic below.

So while it now cycles fine and I had no FTF, I'm still thinking I have a slight undergassed issue. Will pull the bolt again and check the gas rings, and it looks like I'll have to remove the gas block and re-check the alignment.

[ATTACH=CONFIG]8191[/ATTACH]

[Drillboss]

Since it's not locking back on the bolt catch, you're undergassed.

What gas block are you running? I had the one Yankee Hill block that needed to jammed back against the shoulder and I stopped reading the instructions too soon.

[madmike66]

Since it's not locking back on the bolt catch, you're undergassed.

What gas block are you running? I had the one Yankee Hill block that needed to jammed back against the shoulder and I stopped reading the instructions too soon.

Alexander Arms low profile gas block. Whenever I can, I buy the gas block from the same manufacturer of the barrel, so as to avoid issues like this.

[madmike66]

Took the gas block off. The gas block left a nice little circle of carbon showing were the port in the block was in relation to the barrel ort. While it covered the barrel port, it was off to the side a smidge...pretty much right on the edge of it. I nudged the block over to align it better and secured it down pretty well. Will see if this ups the gas pressure enough. If not, there was some carbon on the outside of the gas tube right where it meets the gas block, and extending back a good centimeter. If the problem persists at the range next time, I may try and "bed" the gas tube in the gas block with some Indian Head gasket compound to provide a better seal right at the block.

[LRRPF52]

I always bed my gas tubes into the gas block to eliminate leakage.

I also measure my distances from gas block journal shoulder on the barrel to center of the port, and rear edge of gas block to center of the gas port in the block, then align my block accordingly on the longitudinal axis of the rifle (along the bore/front-to-back). I also clock the gas block once the tube is mounted, to align best with the carrier key with the bolt and cam pin removed, upside down.

[madmike66]

I always bed my gas tubes into the gas block to eliminate leakage.

I also measure my distances from gas block journal shoulder on the barrel to center of the port, and rear edge of gas block to center of the gas port in the block, the align my block accordingly on the longitudinal axis of the rifle (along the bore/front-to-back). I also clock the gas block once the tube is mounted, to align best with the carrier key with the bolt and cam pin removed, upside down.

Thanks, you're always a fountain of great info.

As I was too lazy to go fight the Saturday crowd at the range, I think I'm going to pull the rail again and bed the tube. No reason not to.

The carbon circle left behind lined up perfectly on the gas port as far as distance from the shoulder goes. As for the other stuff you mentioned, greek to me. Link to the procedures you're talking about? Always open to things that'll make my builds better.

[madmike66]

OK, so I finally got to the range to test fire again. As stated, I removed and re-aligned the gas block, and I bedded the gas tube in the block to ensure no gas leaks. The good news is, the rifle now cycles ammo flawlessly. No issues feeding the next round. The bad news is, it locks fully to the rear about 50-60% of the time on an empty 10 rounder, and not at all on the 17 rounder...always the same it locks halfway back on an empty.

I do not think this is a gas issue, unless it is possible I am overgassed. I'm thinking the culprit is the e-Lander magazines. I'm going to order something else and see if I have the same issue. It might be that I'm getting drag on the feed lips. Other possible culprit could be the BCG. I might try swapping that for another and seeing if that helps. And lastly, I might try breaking down and cleaning/relubing the magazines.

It's frustrating, but not a dealbreaker. The rifle performs well, shoots great, and feeds great now. If the only issue is locking back on an empty, I could live with it, as this isn't a combat rifle. Still, I want to get to the bottom of it.