View Full Version : Help diagnosing multiple issues today
I was having a few different issues with one of my ARs today while shooting groups at 50m. The first was that the trigger wouldn’t move, almost like the gun was on safe. I’ve had a popped primer get under there before and this felt very similar to what I remember of that, so between that and how dirty my lower is, I assume that’s the cause of that issue. The next though, I’m not sure of. There were two-three times where I’d pull the trigger, and it’d break, but the round didn’t fire. I took a look and couldn’t see any sign of a primer strike. The lower is filthy but the upper is not, so I wouldn’t expect that there is gunk in the firing pin channel. I also had a round get stuck in the chamber that I had to mortar to get out. That was new Hornady Black 75gr ammo so I wouldn’t expect it to be the problem. Finally, there was one-two feed issues but I don’t really remember the specifics because I have a habit of just tap racking and going, instead of diagnosing the problem.
I don’t know what ammo the other problems happened with, but all of it was some type of OTM and the cheapest was 75gr PPU.
If anyone has any insight on the non-existent primer strikes and the stuck round, I’d appreciate it. I just included the other stuff for more info, though I haven’t yet confirmed that there is an obstruction under my trigger so that one could still be a mystery as well. I’d rather not mention the manufacturers so that I can reach out to them first, if it is deemed that some of this could be issues with at least part of the gun.
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What are the specs on the rifle in question?
The trigger not moving sounds almost assurdly to be a popped primer obstructing movement. It also could be the reason why you had the trigger fall, but no indented primer marks on the brass.
A few years back I was shooting some CBC 62gr in my SPR. Its chamber is darn near minimum headspacing. CBC was defective and some rounds were over max. That caused failure to fire followed by having difficult extraction and sometimes having to mortar the unfired round out. Had to stop shooting the CBC in the SPR.
Not sure if this is what happened in your case, but something to think about if you get a failure to fire followed by difficult extraction.
What are the specs on the rifle in question?
The trigger not moving sounds almost assurdly to be a popped primer obstructing movement. It also could be the reason why you had the trigger fall, but no indented primer marks on the brass.
The primer stopping up my trigger happened three years ago so it’s hard to say for sure, but it definitely felt similar from what I remember. I know that was the case then because I was at a RB1 class asked Jason what was going on. Sure enough, we shotgunned the rifle and pulled out a primer.
As far as specs, the lower is a Noveske that came with an SD-E installed. It’s seen three different primary uppers as well as some others every now and then so I don’t have a close round count but it’d be between 6-8k with very little having been changed in a lot of that time. I did put the A5 system on years ago. Not sure what the life is like for the green spring that’s in there but I did swap between an A5-2 and A5-3 and still had at least one of the malfunctions.
The upper was brand new, I shot it for the first time today. Part of me wondered if it was just break-in, even though that’s not supposed to be a thing. Eventually I did swap it to another lower and didn’t have any more problems. Round count was maybe 40-50 on the Noveske lower and then at least that many on my backup Aero lower.
A few years back I was shooting some CBC 62gr in my SPR. Its chamber is darn near minimum headspacing. CBC was defective and some rounds were over max. That caused failure to fire followed by having difficult extraction and sometimes having to mortar the unfired round out. Had to stop shooting the CBC in the SPR.
Not sure if this is what happened in your case, but something to think about if you get a failure to fire followed by difficult extraction.
I think I fired seven different rounds through it. Once it had an issue with more than one, I stopped paying attention to what ammo was causing problems. Rounds from all of the same boxes were fired out of the same lower two weeks ago and between three different uppers without issue.
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Have you cleaned and inspected the parts?
Is the Hornady ammo to spec, verified COAL not over max?
Could have a short leade?
I’d be cleaning and inspecting as above.
This is hard to actually diagnose, since you cleared some issues and moved on and then swapped stuff around. You need to go back to ground zero and start over. I will tell you that I have had issues with PPU 75gr. ammo in the past. It was blowing primers quite frequently. I think it was due to the primers not being staked right, and not due to pressure.
I would put everything back to zero, and then start with quality known ammo that you know 100% works without issue.
Sure enough, lodged under the hammer spring.
https://uploads.tapatalk-cdn.com/20190617/ec0f1da4f3a603309cfb3b714836fba5.jpg
I haven’t seen anything on inspecting, but did notice when I first got it that the bolt doesn’t easily return to battery when hand cycling. I didn’t think much of it since that was just by hand, but it’s still doing it now and I’m wondering if maybe there’s a bur in there somewhere or something else is going on between the bolt and barrel extension.
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Is the Hornady ammo to spec, verified COAL not over max?
Could have a short leade?
I’d be cleaning and inspecting as above.
No idea, I only had four rounds. That ammo was used by someone else to test my other upper’s accuracy so I just had what was left over from the box.
This is hard to actually diagnose, since you cleared some issues and moved on and then swapped stuff around. You need to go back to ground zero and start over. I will tell you that I have had issues with PPU 75gr. ammo in the past. It was blowing primers quite frequently. I think it was due to the primers not being staked right, and not due to pressure.
I would put everything back to zero, and then start with quality known ammo that you know 100% works without issue.
The more I’ve grouped the stuff, the less impressive it’s been. That being said, this was a 1k round case and I’m down to maybe three hundred rounds and have never noticed a problem before, though not sure I would have. That being said, I assume blown primers would be 100% ammo related right?
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Not returning to battery would explain the no-fires.
Sure enough, lodged under the spring.
https://uploads.tapatalk-cdn.com/20190617/ec0f1da4f3a603309cfb3b714836fba5.jpg
I haven’t seen anything on inspecting, but did notice when I first got it that the bolt doesn’t easily return to battery when hand cycling. I didn’t think much of it since that was just by hahd, but it’s still doing it now and I’m wondering if maybe there’s a bur in there somewhere or something else is going on.
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I'm not saying this super critically - the trend is to shot AR's whole bunches without cleaning, just keeping them well-lubed - I think folks missed that the point of Filthy-Fourteen.
I'd give the rifle a good, thorough cleaning. lube it up, and start from there.
Did you have to take out the FCG to get the primer out?
Not returning to battery would explain the no-fires.
You know I usually incorporate a press check and tap on the forward assist after doing an admin reload but have gotten away from that. Looking back, I know for a fact that I pulled the CH before checking to see if the bolt was fully in battery on those no fires. One of them was definitely with good ammo too, FGMM maybe. I know it wasn’t the PPU because I was shocked that it happened with the good stuff I was shooting.
I'm not saying this super critically - the trend is to shot AR's whole bunches without cleaning, just keeping them well-lubed - I think folks missed that the point of Filthy-Fourteen.
I'd give the rifle a good, thorough cleaning. lube it up, and start from there.
Did you have to take out the FCG to get the primer out?
No, but I did have to use a long Allen wrench because it was definitely wedged in there. The lower is undoubtedly dirty but the upper is brand new.
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Unless you've shot literally thousands of suppressed rounds, a dirty lower is not going to cause any problems. It certainly didn't cause any of OPs problems in question imho.
I've shot about 100rds thus far of Hornady Black 75gr. as it's exceptionally accurate in my barrels, and haven't had any blown primers.
If it's your new KAC, then the A5 setup with the A5H2/A5H3 buffers might be a bit too heavy. KAC uppers are finely tuned. I tried my Mod1 upper on a lower with a H2 buffer and it was no bueno with AE223. Switched back to the factory lower(SR15 buffer is ~2.96oz) and the problems went away.
Unless you've shot literally thousands of suppressed rounds, a dirty lower is not going to cause any problems. It certainly didn't cause any of OPs problems in question imho.
I've shot about 100rds thus far of Hornady Black 75gr. as it's exceptionally accurate in my barrels, and haven't had any blown primers.
I’m sure that primer came from the PPU. That stuff has not grouped too well in any of my guns and has had a good amount of fliers so I’m sure it was the problem there. My response to IG above was just saying that up until that point, I would’ve considered it known quality because the function had been fine for most of a case.
If it's your new KAC, then the A5 setup with the A5H2/A5H3 buffers might be a bit too heavy. KAC uppers are finely tuned. I tried my Mod1 upper on a lower with a H2 buffer and it was no bueno with AE223. Switched back to the factory lower(SR15 buffer is ~2.96oz) and the problems went away.
If that was the case, wouldn’t it struggle to lock back on an empty mag? I thought that was usually the first indicator of too much buffer. Also, that wouldn’t explain the round getting stuck in the chamber would it?
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If it's your new KAC, then the A5 setup with the A5H2/A5H3 buffers might be a bit too heavy. KAC uppers are finely tuned. I tried my Mod1 upper on a lower with a H2 buffer and it was no bueno with AE223. Switched back to the factory lower(SR15 buffer is ~2.96oz) and the problems went away.
I picked up one of the KAC stripped lowers a year or to ago and read a lot about this issue. I built it with the carbine extension with KAC buffer. No problems at all with the SR15 upper and runs like a top.
My understanding was that the 14.5s need the KAC buffer, so they come with it, but the 16s don’t.
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I'd give the rifle a good, thorough cleaning. lube it up, and start from there.
Worth repeating. It's amazing what a good cleaning and lubrication does for these kind of issues. Also, with 6-8K on the lower it's probably time for some fresh springs just as a PM measure.
Worth repeating. It's amazing what a good cleaning and lubrication does for these kind of issues. Also, with 6-8K on the lower it's probably time for some fresh springs just as a PM measure.
Is it worth repeating a third time that the upper is brand new? Or do you believe that it really does need to be cleaned that thoroughly after receiving from the factory?
I agree on the springs though, I actually just pulled my buffer spring and compared it against a new one. It’s about half an inch short. My assumption is the same as above though - if it was a buffer/spring issue, then wouldn’t I be likely to have failures to lock back on an empty mag? And it doesn’t explain the round stuck in the chamber?
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vicious_cb
06-17-19, 17:27
This is hard to actually diagnose, since you cleared some issues and moved on and then swapped stuff around. You need to go back to ground zero and start over. I will tell you that I have had issues with PPU 75gr. ammo in the past. It was blowing primers quite frequently. I think it was due to the primers not being staked right, and not due to pressure.
I would put everything back to zero, and then start with quality known ammo that you know 100% works without issue.
Very odd. How recent were the lots? Ive fired maybe 7-8k rounds the stuff both green and blue box and only had 2 failures, one popped primer and one bullet setback.
A few years for sure. I dumped it after I saw issues as I wasn't in need of another kaboom.
Very odd. How recent were the lots? Ive fired maybe 7-8k rounds the stuff both green and blue box and only had 2 failures, one popped primer and one bullet setback.
Is it worth repeating a third time that the upper is brand new? Or do you believe that it really does need to be cleaned that thoroughly after receiving from the factory?
I agree on the springs though, I actually just pulled my buffer spring and compared it against a new one. It’s about half an inch short. My assumption is the same as above though - if it was a buffer/spring issue, then wouldn’t I be likely to have failures to lock back on an empty mag? And it doesn’t explain the round stuck in the chamber?
Slow down cupcake, my post was general advice and not a diagnosis. But yeah, pulling the BCG apart and giving it a quick wipe down, visual inspection and lube isn't the worst thing you could do for a "new" upper before putting it into service. At the very least it's another variable eliminated.
Slow down cupcake, my post was general advice and not a diagnosis. But yeah, pulling the BCG apart and giving it a quick wipe down, visual inspection and lube isn't the worst thing you could do for a "new" upper before putting it into service. At the very least it's another variable eliminated.
I did that. I don’t know if it’s showed up in any of my posts because Tapatalk kept crashing and making me re-write them, but it was done.
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So your problems went away when you switched lowers? Or are you still getting the same problems with the lower you switched to?
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So your problems went away when you switched lowers? Or are you still getting the same problems with the lower you switched to?
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The locked trigger went away but that was it. It’s going in for warranty work today. I reached out to the manufacturer to get their thoughts and they didn’t hesitate to say they wanted to take a look.
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Got the upper back from KAC today. They shipped it back to me on the 11th business day which is pretty damn good considering that I assume they’re working on contracts right now since uppers are OOS everywhere. Similar to my BCM last week, there was no indication of what was done to it. I know it’s the same rail because I can see where my grip and light were mounted, but that and the barrel at least got a healthy amount of oil. I didn’t look at the receiver much though, I was far too distracted by the shiny new sandcutter carrier that was inside... I was pretty surprised to have an issue from the factory, but it’s a good reminder that it’s always possible. Seeing as how I’ve had to send a few expensive things back in the last year or two, I’m very happy with how they handled it.
Ultimately I think I’m going to replace it with a 14.5, just because this is my only 16” gun and while I had reasons for trying it, that extra inch doesn’t feel worth it when paired with the Razor and M600DF.
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