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-ASS 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 (https://www.dropbox.com/s/guus0opqkhiuhl0/video%20may%2016%2C%2010%2059%2016%20am.mov?dl=0)

In Battery Photo (http://steamforge.net/img/in_battery.png)
Out of Battery Photo (http://steamforge.net/img/out_battery.png)

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 3 O'Clock with lots of rotation. 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

[Computalotapus]

If you have another rifle start with swapping the BCG for one that you know you don't have issues with. If it works then swap the extractor spring and bushing.

[Dstrbdmedic167]

Agree with comp. Also what ammo were you using? New or reman new?

[GaSwamper]

Welcome Scout, good job on presenting your problem alota guys say " hey I got a problem. Whats wrong?" lol. I agree to swap the BCG to one you know functions right first. If that doesn't fix then maybe swap the heavy buffer to standard. Of course a quick check of the gas block to make sure everything is lined up, I doubt port size issues but ya never know. What ammo were you running and have you tried different brands/loads?

[GaSwamper]

Agree with comp. Also what ammo were you using? New or reman new?

I type too slow!

[Dstrbdmedic167]

I type too slow!

No you just made a better quality post.

[alamo5000]

Upon thinking about it more there could be a number of issues.

Here would be my non expert check list.

As others have said ammo. If it is out of spec it won't seat all the way in the chamber and will create gas leaks which could chain react to short strokes or whatever.

Possible head spacing check? Inspect the chamber of your barrel.

Make sure the gas block isn't moving around under pressure.

Obviously check the bolt/swap it to see if the problem persists as others have already said.

[Stone]

Re-check headspace(assuming you did a first time) Cycle the rifle a few hundred times by hand. Give the chamber a good scrub down and try some different ammo...

[Eric]

try some different ammo... Exactly. One of the first things to look at for something like this, especially if reloaded/remanufactured.

Next up would be to try a different complete BCG. Confirm the gas key is not binding up on the gas tube.

Always start troubleshooting with a clean and well lubed rifle. Hit the chamber with a chamber brush, ensure there isn't something wedged in the chamber or lugs, like a primer chunk.

[Stone]

"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."
Are you 100% sure that those 2 rounds fully seated in the chamber? When you mortared the rifle did it pull the round out?

[SINNER]

How many rounds were in the magazine at the times of failure? I have seen a too weak buffer spring cause this very issue only when mags are near capacity. The drag on the bolt from the pressure of the rounds below slows it down enough to cause it not to go into battery.

Did you attempt to use the forward assist to get the bolt into battery?

If not that I would look hard at the fitment of the extractor in the bolt. A bolt machined on the small side of the spec with coatings applied can and will restrict the movement of the extractor although if that was the case it would normally cause issues from the onset and not be so random. Also when the extractor is restricted it will normally cause damage to the rim of the round.

[Scout Actual]

BINDING
The bolt runs smoothly in and out. I opened it up and ran the bolt forward and back by hand it felt smooth. I can push the bolt into battery with one finger.

HEADSPACE
I checked the headspace when I first built it and again just now using Forester GO (1.4636 MIN) & NO-GO (1.4736 MAX) gauges. It goes into battery on the GO and won't go into battery on the NO-GO. I have not ever tried to actually measure the specific headspace value (on any AR).

AMMO
I was using remanufactured brass .223. I didn't try other ammo. I will when I can

BCG
I CAN swap BCGs but I didn't. I will when I can.

EXTRACTOR
The extractor is difficult to actuate. In fact, I can't get the retaining pin out. I have a DD bolt that is easier to actuate and I was able to get the retaining pin out easy-peasy.

MAGAZINE
I can't know for sure right now, but judging from the video. There were probably 19 rounds in the magazine + 1 in the chamber. I know which magazine I was using on one of the instances of failure but not the other :/

[Dstrbdmedic167]

I'm going with improperly sized brass since it was reman ammo. I've had a similar issue and realized my die got off and wasn't reforming the brass enough. Had a time with it until I figured out that's what it was.

[Jerry R]

AMMO
I was using remanufactured brass .223. I didn't try other ammo. I will when I can


This is a flag I see based upon only two failures in the batch. If a case is not resized properly (or not at all) and had been fired in a max spec (or out of spec) chamber they can "bind" in a chamber that is minimum spec or close to it.

Totally unrelated --> If you get into reloading, I would suggest an RCBS Small Base 223 sizing die since you have multiple chambers you will be reloading for. This die sizes to factory minimum specs and rounds will drop into any spec chamber. Will shorten case life a little, but reliability is more important to me than one or two extra reloadings on a case.

Let us know when you try different ammo - would try factory only until problem determined.

[Scout Actual]

It will be at least 2 weeks until I can get outdoors to shoot :( I can probably get to an indoor range this week. Hopefully I will be able to do the comparison effectively in the little booth. FYI I own two different brands of remanufactured ammo and I will buy some factory ammo and compare all 3 ejection patterns.

I can also try the remanufactured ammo in another rifle with a new DD barrel and another with a 1000 round DD barrel.

[VIPER 237]

First take out that ST-T2 buffer and throw in a real H2. I have seen that POS make perfectly reliable carbines an instant jam-o-matic, and many have experienced the same issue that you are describing.

[velocity2006]

I would try to try a few different brands of factory quality brass cased ammo before pulling any parts off of the rifle. Is it possible to find out of the re-man ammo was made with a full length or small base sizer? When I load for my ar's I specifically use small base dies, using FL dies can cause the issue your are experiencing.

[gatordev]

First take out that ST-T2 buffer and throw in a real H2. I have seen that POS make perfectly reliable carbines an instant jam-o-matic, and many have experienced the same issue that you are describing.

I'm curious, what makes the ST-T2 specifically unreliable? My understanding is that it's just a buffer with a weight in between a H and H2 buffer. If something doesn't work with it, wouldn't it be more about an incorrectly ported barrel for the length and/or ammo? By the same logic, I've heard of people not being able to cycle a round after using a H2 buffer, but again, you can't really blame the type of buffer itself for the failure, just that it's too heavy for the setup.

Please understand, I have no emotional tie to the T2 (I do own one as my first lower was a factory Spike's from years ago) and I run mostly H2s with a few Hs, I'm just curious about the reasoning.

[SINNER]

I have heard the e-myths about the ST-T2 causing issues but have never seen it myself. Usually it's just too heavy of a buffer for the use and most people not having a clue to the effect of changing buffer weights. IE changing out a carbine buffer with a Spikes heavy that will not run and then blaming the buffer. I have asked and asked to be shown where a gun will run a H buffer but not the Spikes and NEVER saw an example. The fact that the ST-T2 is actually slightly heavier than a standard heavy buffer likely has not helped the uneducated who assume it's identical to a normal H buffer.

[Scout Actual]

I'll be taking a variety of ammo and a couple rifles to the range soon to compare & contrast. After that I may swap out Buffers if it makes sense.

[VIPER 237]

The reciprocating mass of a standard buffer design (3 weights separated by rubber pads) helps reduce bolt bounce. The Spikes ST-T2 has been shown to increase bolt bounce over a standard buffer design. I have personally seen carbines run with an H or H2 buffer that would not run reliably with a ST-T2. It is more prevalent in a Full Auto as you have more carryover forces from one shot to another but the concept is true for semi's as well. I have found on many occasions that when a person is having problems similar to what the OP is stated, they are solved by switching to a standard buffer design.

I stole this off of Arfcom as it is one of the best explanations I've found.

'Bolt bounce is reduced by the buffering motion of the internal weights in the buffer (that's why it's called a "buffer"). In a standard carbine length buffer there are three internal weights separated by rubber pads. The successive movement of the weights creates a long duration "push" on the bolt carrier as it closes in order to prevent or limit its "bounce" and hold it against the barrel extension. An often overlooked function is that the same process works at the back of the function cycle, when the buffer and BCG reach the back of the buffer tube. At that point, the buffer tries to hold the BCG at the back of the tube momentarily instead of it bouncing forward... this gives more time for the ejected case to clear the ejection port, the ammo stack to rise and settle in the magazine, the bolt catch to rise on the last round, etc.

It also buffers the opening and unlocking sequence of the BCG to smooth that process out and reduce impulse loading on the bolt and cam pin.

All of those work in concert, since if the last two functions are "buffered" this reduces the BCG velocity and the cyclic rate, so there is less bolt bounce on closing that needs to be controlled.

The Spike's buffer is different in that is just has a mass of small pellets as moving internal weight instead of the individual weights and rubber spacers. This design means that there is just one delayed spike (no pun intended) of force from the buffer instead of the long duration push of the multiple weights from a standard buffer.'

[gatordev]

Ahh, okay, so it's a different design and not just weight. Gotcha. Thanks. I thought I remembered there was something "different," but didn't realize it was a different take on what would initially appear to be the same idea.

[SINNER]

My limited knowledge of physics tells me that those weights in a buffer will act as a single weight at the velocities experienced during firing. As will the powder to a lesser extent only because the powder lacks a hard face to impact the buffer internally. The clearance in the buffer that allows the weight to travel a short distance from end to end provides the deadening affect. Just like a dead low hammer that is filled to capacity is no longer a dead blow hammer, if you remove the open space it will no longer provide any dampening.

I have no reason to say the Spikes is better or worse. To the contrary I have found NO difference in the function of a rifle with or without the spikes buffer installed when you match the weights. I see the Spikes buffer as a invented fix for a non-existent problem honestly.

[alamo5000]

It will be at least 2 weeks until I can get outdoors to shoot :( I can probably get to an indoor range this week. Hopefully I will be able to do the comparison effectively in the little booth. FYI I own two different brands of remanufactured ammo and I will buy some factory ammo and compare all 3 ejection patterns.

I can also try the remanufactured ammo in another rifle with a new DD barrel and another with a 1000 round DD barrel.

I feel your pain. I haven't been able to shoot for a while now. We had a family member pass away and have been housing a few people and planning a funeral. It's been a house full of people from all over for a week. Tomorrow is the ceremony. (FWIW It was my grandmother and she was like 93 years old so it's not like it was unexpected)... but everyone is doing fine if anyone is wondering.

Not that we know that ammo is the problem---but to me it's a real contender...but do you mind telling us what kind of ammo you were running? Or was it just some home spun local kind?

In the process of my reloading I got a bunch of random brass that I was resizing and trimming for a while there. I was actually surprised at just how deformed the brass can get. If the brass is of a very soft variety and it was fired in a slightly larger chamber it's likely that that ammo might not even seat well in a standard chamber. And the length of the brass was also very instructive. The brass was very stretched out length wise in some cases.

I would be curious as to what you figure out so please keep us updated.

[GOST]

Hate to hear that about your grandmother.

[SINNER]

Hate to hear that about your grandmother.

X2 Sorry for your loss.

And I do not suspect ammo as the cause if in fact the extractor was not capturing the rim. Even if the case sticks halfway into the chamber the extractor should still engage the case.