Erratic Ejection Angle + Bolt Locked behind Live Round

[Scout Actual]

Hello all,

I've got a problem I'd like some help with. I just recently built a new AR-15 from the ground up. My experience level is that I've built 2 AR's from the ground up (except drilling/reaming taper pin for FSB/Gas Block) and done modifications to a DD rifle. The parts of interests are Spike's Tactical with a DD Barrel, DD Gas Block, and Geissle SSA Trigger. Complete parts List below:
- Spike's Tactical FDE Stripped Lower/Upper combo (FA & Cover installed)
- Spike's Tactical LPK (minus fire control group)
- Spike's Tactical T2 Buffer, Buffer Tube, Spring, QD Receiver Plate, Castle Nut, Melonited Gas Tube
- Spike's Tactical NiB BCG
- Geissele SSA Trigger Group
- Daniel Defense Lightweight profile, Mid-length, CHF, Chromed, 16" 1:7 Barrel
- Daniel Defense Superior Suppression Device
- Daniel Defense Low Pro Gas Block
- BCM KMR13, Cerakoted Magpul FDE @ Dobb's Defense
- Magpul MBUS Sights
- Magpul STR Stock, FDE
- AXTS Raptor Charging Handle
- Troy Ambi Mag Release
- BAD-*** Ambi Safety w/ Standard & Hybrid Lever
- Stark SE-1 Grip
- Vortex StrikeFire Non-Magnified Red Dot
- ErgoGrip Keymod Enhanced Angled Grip
- Noveske QD Direct Attach Swivel Mount

I took it out for the first time yesterday and at first I thought everything was fine. However I had two instances of the same failure (in a total of about 200 rounds fired). During a string of fire (perhaps 0.5 seconds between rounds, plenty for everything to settle) I had the bolt lock up in a mostly closed position. The bolt is about 1/8" out of battery. There was a live, unfired, round in the chamber at this time. The field expedient fix was to mortar the gun to let inertia loosen the bolt.

Luckily a friend happened to be filming me while this happened. See slow-motion, 240 FPS, Dropbox video below (pay no mind to my terrible trigger reset... I'm a relative newb). Also I've screen-grabbed & cropped a pic of the bolt in battery during normal operation and out of battery (basically the failure) shown below.

Dropbox: Slow-Motion 240 FPS Video

In Battery Photo
Out of Battery Photo

Speaking to a few guys at the range a conclusion was reached that, in the failure case, the bolt is closing on the round without the extractor making it over the rim of the cartridge but is rotating enough be stuck. Some suggested that there might be wrong with the extractor spring and that it should be replaced. Since it is such a cheap fix I already have new springs (mil-spec Spikes in old case, David Tubb springs in the new case) on order.

After looking at the video evidence it is also obvious that I've got erratic and inconsistent ejection. Sometimes the rounds eject at 5 O'Clock with little rotation, sometimes they eject at 2 O'Clock with lots of rotation and everywhere inbetween. Could these 2 problems be related? Could the gun be undergassed and that is why the extractor sometimes doesn't make it over the case rim?

Thanks in advance!
Scout

 

[Keith Glasscock]

Since nobody has replied, I'll share some observations.

First, the bolt carrier is moving full travel during each cycle. I can even see the recoil impulse when the buffer strikes the end of the tube. In other words, no, you are not under gassed.

When the bad round chambers, I notice that the forward movement of the carrier is much slower than prior shots.

I also notice that the bolt is jammed - this means that the extractor engaged.

My first place to look would be at the brass to chamber fit. What did you do with the rounds that jammed? If you fired them later, did they chamber normally?

I'd try different ammo first to see if that has anything to do with it. If you are running reloads, it could be a sizing issue.

Best of luck

 

[nilebartram]

correct buffer and spring?

 

[minnesotamulisha]

Check to see if there is lube or debris in the chamber. On my first build, I applied too much grease and it wasn't allowing the round to chamber completely. Some would, some wouldn't.

 

[Minesweeper3433]

I would also check your chamber. You may have bought a nice Daniel Defense barrel but that doesn't mean there is no chance of something being wrong. And there has been a lot of bad barrels coming from smaller shops in the last few years due to the ultra high demand for them and low supply. I've seen undersized chambers and out of headspace chambers, poorly cut chambers and oversized/wallowed out.