Failure To Go Into Battery. But Why..?

MODiesel · #1 03-10-11, 16:27

All:

First, sorry for the length, but I wanted to try and provide as much detail as possible...

I've got a name brand, high-quality 14.5in (pinned) carbine upper that recently had a series of failures of the bolt to go into battery. We've had the rifle about a year and have probably put about ~600rds through it. The failures happened on a damp, 40F day, after shooting only ~700 rounds through it, with well under 250 rounds since the last, thorough cleaning. We didn't take any pictures as the day was getting colder and we had been shooting for hours -- just kind of tired at that point. But the failure was odd, and wasn't something I could easily sort out, so I'll try and describe here in detail. Maybe someone has an idea...

The problem occurred out of nowhere. Ammo was a mix of Silver & Brown Bear 62gr HP, though the culprits here were Brown Bear. Magazines were USGI that a cousin brought back with him from Iraq. After two full mags, only about ~10 rounds had been fired out of a third magazine when the rifle went "click." Muzzle safety was the immediate order, but we quickly realized that the bolt had not locked up. Through the ejection port, you could see the lugs were still hung up in the "star chamber" of the barrel extension. From what I understand, that means the cam had not yet rotated the bolt though it's possible that it might have just started to, before the lugs had fully seated in the barrel extension. Anyway, the forward assist didn't feel like it was engaging any of the carrier notches and was ineffective. However, strong pressure on the charging handle also couldn't budge the carrier. Ultimately, I had to collapse the stock and mortar the rifle only moderately against my thigh (not the ground). After a few attempts, the BCG released and actually ejected the unfired round. The bullet on that round had a noticeable, sharp gouge in the side of the jacket, about 1/2 way down the bullet. Our immediate thought was "bad ammo." So after cycling the BCG a few more times, we tried again with the same magazine. With the BCG against the stop, I hit the bolt release only to find the exact same scenario. The bolt was once again hung up in the lugs of the barrel extension. That resulted in the same mortar procedure and the offending round once again was properly ejected. This round had a deep scratch on the case, and what looked like a gouge right at the case mouth joint with the bullet. Hmmm...

At this point, we figured it was more than just the ammo. We broke it down and looked in the barrel and barrel extension but could find no obstructions or large debris. There was a scattering of tiny, fine metal shavings in the star chamber from what looked like the extractor sharply grabbing the case rim, but my other (16in middy) AR does the same thing so I didn't think much of it. The gas tube did not show any signs of "conflict" with the carrier key, and the key had nothing stuck in it. We tore down the BCG, and while it was dirty we couldn't find anything wrong. We generously wiped everything down with CLP, but our vet cousin really thought the gas rings were fitting too tightly. Indeed, they were pretty tight, but you could still make the bolt slide and turn in the carrier. We buttoned it all back up, generously lubed, and tried to chamber a round from a different magazine (same ammo). Same result....and the rifle was unloaded and cased up for the day.

Later, I tore it back down to try and figure it out. Some add'l specs for those wondering:

14.5in Carbine Barrel
Full Auto BCG ** Complete BCG was provided with the receiver **
MPI Bolt
Blue Insert with O-Ring
H buffer
M4 Stock w/Unknown Buffer Spring

Upon further inspection, I tried cycling a few more rounds with some of the same ammo, but different mags. Three consecutive times I got the same result -- bolt hanging before going into battery, but could be mortared and would eject each round. At that time, I also grabbed a good PMag loaded with Hornady 5.56 75Gr T2 rounds. I tried cycling two of those rounds and got the same result. Some of these rounds looked like they had odd scratches on the bullet jacket, but it's hard to tell those apart from the normal scratches that come from ejecting a loaded round.

Since then, I've cleaned the cwap out of it but have not yet shot it again. I scrubbed on the BCG, the barrel extension and the chamber until nothing wipes out. I could find no obstructions, nor can I find any part that is amiss (compared to the other AR). I pulled the buffer spring to make sure it was still in spec, and that was fine. Nothing was binding there, and there is no additional wear in the receiver extension. Of course it now loads any ammo from any mag, with no issue. I can drop the bolt on a fresh mag and it chambers just fine. If I cycle the BCG a few times there are no issues. And before it gets mentioned, there would be almost no way for the chamber to be out-of-spec. Per the forum rules, I won't name names, but this is a top tier barrel. I understand anything can have faults, but it's also been flawless for about a year or so with all sorts of rounds through it. That's what makes this "out-of-nowhere" failure so odd.

The one thing that may have some merit though, is, possibly, the gas rings. When I compare this to my other AR, I can simply drop the BCG within the upper receiver by hand, and the bolt will lock up in battery. If I do that with the rifle in question, the bolt will not lock up completely. I have to push the BCG a bit. That's after I had cleaned both and generously lubed both BCG assemblies.

Given all of that, where would you guys look? The ammo is obviously cheap, but we were firing it out of the other rifle without issue and this is the first time any of the "Bear" ammo hasn't worked 100% for me. Could the gas rings have just expanded or worn out in such short time? Could a tight bolt/carrier fit cause this issue? If so, which is the more likely culprit? This rifle is otherwise my wife's SHTF carbine and she loves the thing. But I want to make sure it's as reliable as possible, and not finding the culprit here is just eating at me. Any advice is appreciated.

Iraqgunz · #2 03-10-11, 16:49

Please tell us what your version of a name brand "top quality" carbine upper is.

Quote:

Originally Posted by MODiesel

All:

First, sorry for the length, but I wanted to try and provide as much detail as possible...

I've got a name brand, high-quality 14.5in (pinned) carbine upper that recently had a series of failures of the bolt to go into battery. We've had the rifle about a year and have probably put about ~600rds through it. The failures happened on a damp, 40F day, after shooting only ~700 rounds through it, with well under 250 rounds since the last, thorough cleaning. We didn't take any pictures as the day was getting colder and we had been shooting for hours -- just kind of tired at that point. But the failure was odd, and wasn't something I could easily sort out, so I'll try and describe here in detail. Maybe someone has an idea...

The problem occurred out of nowhere. Ammo was a mix of Silver & Brown Bear 62gr HP, though the culprits here were Brown Bear. Magazines were USGI that a cousin brought back with him from Iraq. After two full mags, only about ~10 rounds had been fired out of a third magazine when the rifle went "click." Muzzle safety was the immediate order, but we quickly realized that the bolt had not locked up. Through the ejection port, you could see the lugs were still hung up in the "star chamber" of the barrel extension. From what I understand, that means the cam had not yet rotated the bolt though it's possible that it might have just started to, before the lugs had fully seated in the barrel extension. Anyway, the forward assist didn't feel like it was engaging any of the carrier notches and was ineffective. However, strong pressure on the charging handle also couldn't budge the carrier. Ultimately, I had to collapse the stock and mortar the rifle only moderately against my thigh (not the ground). After a few attempts, the BCG released and actually ejected the unfired round. The bullet on that round had a noticeable, sharp gouge in the side of the jacket, about 1/2 way down the bullet. Our immediate thought was "bad ammo." So after cycling the BCG a few more times, we tried again with the same magazine. With the BCG against the stop, I hit the bolt release only to find the exact same scenario. The bolt was once again hung up in the lugs of the barrel extension. That resulted in the same mortar procedure and the offending round once again was properly ejected. This round had a deep scratch on the case, and what looked like a gouge right at the case mouth joint with the bullet. Hmmm...

At this point, we figured it was more than just the ammo. We broke it down and looked in the barrel and barrel extension but could find no obstructions or large debris. There was a scattering of tiny, fine metal shavings in the star chamber from what looked like the extractor sharply grabbing the case rim, but my other (16in middy) AR does the same thing so I didn't think much of it. The gas tube did not show any signs of "conflict" with the carrier key, and the key had nothing stuck in it. We tore down the BCG, and while it was dirty we couldn't find anything wrong. We generously wiped everything down with CLP, but our vet cousin really thought the gas rings were fitting too tightly. Indeed, they were pretty tight, but you could still make the bolt slide and turn in the carrier. We buttoned it all back up, generously lubed, and tried to chamber a round from a different magazine (same ammo). Same result....and the rifle was unloaded and cased up for the day.

Later, I tore it back down to try and figure it out. Some add'l specs for those wondering:

14.5in Carbine Barrel
Full Auto BCG ** Complete BCG was provided with the receiver **
MPI Bolt
Blue Insert with O-Ring
H buffer
M4 Stock w/Unknown Buffer Spring

Upon further inspection, I tried cycling a few more rounds with some of the same ammo, but different mags. Three consecutive times I got the same result -- bolt hanging before going into battery, but could be mortared and would eject each round. At that time, I also grabbed a good PMag loaded with Hornady 5.56 75Gr T2 rounds. I tried cycling two of those rounds and got the same result. Some of these rounds looked like they had odd scratches on the bullet jacket, but it's hard to tell those apart from the normal scratches that come from ejecting a loaded round.

Since then, I've cleaned the cwap out of it but have not yet shot it again. I scrubbed on the BCG, the barrel extension and the chamber until nothing wipes out. I could find no obstructions, nor can I find any part that is amiss (compared to the other AR). I pulled the buffer spring to make sure it was still in spec, and that was fine. Nothing was binding there, and there is no additional wear in the receiver extension. Of course it now loads any ammo from any mag, with no issue. I can drop the bolt on a fresh mag and it chambers just fine. If I cycle the BCG a few times there are no issues. And before it gets mentioned, there would be almost no way for the chamber to be out-of-spec. Per the forum rules, I won't name names, but this is a top tier barrel. I understand anything can have faults, but it's also been flawless for about a year or so with all sorts of rounds through it. That's what makes this "out-of-nowhere" failure so odd.

The one thing that may have some merit though, is, possibly, the gas rings. When I compare this to my other AR, I can simply drop the BCG within the upper receiver by hand, and the bolt will lock up in battery. If I do that with the rifle in question, the bolt will not lock up completely. I have to push the BCG a bit. That's after I had cleaned both and generously lubed both BCG assemblies.

Given all of that, where would you guys look? The ammo is obviously cheap, but we were firing it out of the other rifle without issue and this is the first time any of the "Bear" ammo hasn't worked 100% for me. Could the gas rings have just expanded or worn out in such short time? Could a tight bolt/carrier fit cause this issue? If so, which is the more likely culprit? This rifle is otherwise my wife's SHTF carbine and she loves the thing. But I want to make sure it's as reliable as possible, and not finding the culprit here is just eating at me. Any advice is appreciated.

MODiesel · #3 03-10-11, 17:02

Quote:

Please tell us what your version of a name brand "top quality" carbine upper is.

Noveske N4

Iraqgunz · #4 03-10-11, 17:50

Your post is kind of hard to follow because it's written as an e-novel. Having said that assuming that you are not riding the bolt forward there is something else going on.

Have you made any silly modifications? Are you seeing any gas leakage? Since it aslo happened with Hornady TAP T2 that leads me to believe that there is something going on with the upper. I would contact Noveske and run it past them.

Maybe Todd will chime in?

nimdabew · #5 03-10-11, 17:58

Can we get pictures of the ammo that was getting hung up in the chamber, the disassembled parts of the BCG, and possibly one of a bore light + chamber shot?

My first impression sounds like you might have a burr in the chamber area.

MODiesel · #6 03-10-11, 19:30

Quote:

Originally Posted by Iraqgunz

Your post is kind of hard to follow because it's written as an e-novel. Having said that assuming that you are not riding the bolt forward there is something else going on.

Have you made any silly modifications? Are you seeing any gas leakage? Since it aslo happened with Hornady TAP T2 that leads me to believe that there is something going on with the upper. I would contact Noveske and run it past them.

Maybe Todd will chime in?

In all cases BCG was released by hitting the bolt release. The only things added to the upper beyond how it arrived are a set of MOE handguards and an optic. And no gas residue around the FSB or gas tube.

MODiesel · #7 03-10-11, 19:33

Quote:

Originally Posted by nimdabew

Can we get pictures of the ammo that was getting hung up in the chamber, the disassembled parts of the BCG, and possibly one of a bore light + chamber shot?

My first impression sounds like you might have a burr in the chamber area.

After we figured out it was the rifle and not the ammo, we popped it in the other rifle (BCM) and it shot just fine. I'll take some shots of the BCG parts if you want. Anything in particular to focus on? And I don't have a a bore light, but I'll see what I can do to get a shot of the chamber. There is nothing obvious in there that I can see with the naked eye, and I can drop cartridges in just fine and they seat with no issue.

Todd.K · #8 03-10-11, 19:47

Did you clean under the extractor?

Try a new action spring if you have one available.

nimdabew · #9 03-10-11, 21:00

Quote:

Originally Posted by MODiesel

After we figured out it was the rifle and not the ammo, we popped it in the other rifle (BCM) and it shot just fine. I'll take some shots of the BCG parts if you want. Anything in particular to focus on? And I don't have a a bore light, but I'll see what I can do to get a shot of the chamber. There is nothing obvious in there that I can see with the naked eye, and I can drop cartridges in just fine and they seat with no issue.

Well I want to see the pictures of the gouges on the ammo itself to see if it was something in your chamber, not generic ammo types you used. As for the bore light, just have a light source on the front of the gun and take a picture of the chamber area from the reat of the upper. I like using a low lumen flashlight like a AA maglite or a surefire on the low setting and set it on the floor with the upper between my knees.

nimdabew · #10 03-10-11, 21:03

Quote:

Originally Posted by MODiesel

After we figured out it was the rifle and not the ammo, we popped it in the other rifle (BCM) and it shot just fine. .

Are you talking about the ammo being in the other rifle or parts of the rifle in another upper? If the upper is fine, then the lower may be messed up if the problem has been isolated to the rifle itself, and the upper is just fine.

evolixsurf · #11 03-11-11, 01:35

sounds like your magazines are shot and its deforming the bullet or case neck badly before entering the chamber... which explains all the shavings. Did you use those same mags in the other gun? I would try with some different ammo too... Let us know.

evolixsurf · #12 03-11-11, 02:16

Also, I would pull apart that bolt and inspect the cam pin and see if you have a primer or something stuck in there.

bp7178 · #13 03-11-11, 03:34

Where did your lower come from? I noticed the OP had info about the upper, nothing about the lower.

IMO, this sounds more like a buffer spring issue. Not enough steam to chamber a round.

MODiesel · #14 03-11-11, 10:43

Quote:

Originally Posted by nimdabew

Are you talking about the ammo being in the other rifle or parts of the rifle in another upper? If the upper is fine, then the lower may be messed up if the problem has been isolated to the rifle itself, and the upper is just fine.

No parts were swapped between the rifles. Other than the one bullet that was really gouged (which we tossed) all of the other "test" rounds shot fine through the other rifle.

MODiesel · #15 03-11-11, 10:45

Quote:

Originally Posted by evolixsurf

sounds like your magazines are shot and its deforming the bullet or case neck badly before entering the chamber... which explains all the shavings. Did you use those same mags in the other gun? I would try with some different ammo too... Let us know.

It's possible, as the USGI mags saw a lot of use in Iraq. But, we were able to shoot the rest of the rounds in the "offending" mag in the other rifle. And I've interchanged the mags between both rifles a number of times without issue. Moreover, the Pmag, which has only seen light use, also had the same issue with the Hornady 5.56 rounds.

MODiesel · #16 03-11-11, 10:53

Quote:

Originally Posted by bp7178

Where did your lower come from? I noticed the OP had info about the upper, nothing about the lower.

IMO, this sounds more like a buffer spring issue. Not enough steam to chamber a round.

The lower is a blemished Noveske, but I'm not even sure what constituted the "blemish."

As for the buffer spring, I'm starting to think this might be the biggest culprit. Paul noted that above, too. As I think it through, it's possible that the spring has just gotten a tad weak and combining that with a dirty bolt/gas rings and a stiff extractor (with the O-ring), it might not have had enough "oomph" to properly pop over the case rim and chamber the round. Then, when it went to lock up, not everything was perfectly in place. Likewise, if the BCG was a touch weak/slow, it could be that the rounds weren't feeding as directly, possible banging off the feed ramps and extension lugs, which would account for the odd bullet marks.

The only flaw in that theory is if the bolt/extractor weren't really grabbing the case rim, then would it properly eject when I finally cycled the carrier? In each case when I got the carrier to move it properly flipped the cartridge out & back with good force. It didn't just fall out of there.

I'll also try and get some bore pics tonight. I just ran out of time last night.

bp7178 · #17 03-11-11, 14:37

An easy solution would be to try it on a known good working lower. Was your lower assembled from parts? Or was it bought as a complete lower? Round count?

MODiesel · #18 03-11-11, 14:41

Quote:

Originally Posted by bp7178

An easy solution would be to try it on a known good working lower. Was your lower assembled from parts? Or was it bought as a complete lower? Round count?

I'll probably try that once I put a few rounds through it again (most likely this weekend). The lower was assembled from parts. Total rounds through the complete rifle is ~700.

bp7178 · #19 03-11-11, 16:04

What brand are the parts and or were they used before they went into the rifle?

Mac5.56 · #20 03-11-11, 16:11

Quote:

Originally Posted by MODiesel

I'll probably try that once I put a few rounds through it again (most likely this weekend). The lower was assembled from parts. Total rounds through the complete rifle is ~700.

I personally don't foresee your buffer spring being spent after that many rounds, but it is always possible. I am not the wealth of knowledge that some people on this site are, but there is an acceptable spring length for a carbine spring, and once it is smaller then this it is time for a replacement.

Use the search to find the length, it should pop up right away. It did for me when I checked a while back.