Blown primers and other malfunction troubleshooting

[markm]

Also, I noticed a primer that was almost dislodged when picking up brass today.

Lately I see so many casings like this, I no longer even give it a thought. It's just a part of shooting for me now.

[1168]

Alright so I have to check my round count since throwing the E-BCG in and dropping the buffer but so far, no malfunctions due to blown primers. Last weekend, I was using the A5H1 (per Criterion CS) and today I went back to the A5H3.

But.

The BCG is having frequent trouble feeding the first round from USGI mags when I hit the bolt release. I believe I’ve had four of these failures between the last two weeks and I didn’t take note of it at the time, but I believe this was with two different lowers. PMAGs have been a non-issue and I’ve had a few USGI mags that were fine, but every stoppage was with GI mags and none of them were the same mag. The round would just start to feed, so I had to rack it every time.

Also, I noticed a primer that was almost dislodged when picking up brass today. I kept most of the other brass but still need to sort through and see if there are others. No way of knowing if this was the same gun or not since I had several out today, but I’m guessing that it is.




And, as I’m shooting faster, I’m noticing more recoil than I’d expect based on my other guns. I don’t have any other 12.5s but between my 11.5 Geissele and several 14.5s (most with the same flash hider and A5 buffer), this thing kicks a bit. I’ve also noticed that it does spit gas in my face more than I’d expect with the KAC QDC, even with the E-BCG.

Finally, rounds have some zip. I chrono’d it today with the same 56gr MEN at an average of 3099.4 FPS and 77gr S&B at 2633 FPS. For reference, my 14.5 Mod2 KAC was at 2984.8 and 2585.4. All five round groups, taken one after another. Between the recoil and gas to face, I’m only a little surprised that it’s pushing rounds with more FPS than a 14.5 barrel.

Super curious on continued thoughts here. Maybe the chamber is just a tad undersized?

ETA - round count was 541 w/ REBCG and is 886 now so 345 rounds with the E-BCG and no fully blown primers.

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For your feeding problem, check your feed ramps for a burr using a Q-Tip. Even good barrel manufacturers fail to catch this sometimes, and it kinda grabs the bullet as it goes up the ramp. Just slip some cotton in and around the lug passage on the feed ramps and see if it pulls.

If that’s not it, its the A5H3. 17k and I have noticed this failure to chamber the first round problem with the A5, and for me it seems more common in the heavier ones. He solved it by removing the bias spring in his, but then reverted to a regular setup. I mostly solved it, unintentionally, by using a lighter buffer, and it only does it when I’m not trying to reproduce the problem.

The popped primers are a pressure problem, and it does not appear that swapping buffers or carriers will fix it. Your chrono results confirm this. Be aware that popped primers only occur after the point of plastic deformation of the case head is overcome by pressure, and occurs at a pressure much higher than “max”.

[georgeib]

For your feeding problem, check your feed ramps for a burr using a Q-Tip. Even good barrel manufacturers fail to catch this sometimes, and it kinda grabs the bullet as it goes up the ramp. Just slip some cotton in and around the lug passage on the feed ramps and see if it pulls.

If that’s not it, its the A5H3. 17k and I have noticed this failure to chamber the first round problem with the A5, and for me it seems more common in the heavier ones. He solved it by removing the bias spring in his, but then reverted to a regular setup. I mostly solved it, unintentionally, by using a lighter buffer, and it only does it when I’m not trying to reproduce the problem.

The popped primers are a pressure problem, and it does not appear that swapping buffers or carriers will fix it. Your chrono results confirm this. Be aware that popped primers only occur after the point of plastic deformation of the case head is overcome by pressure, and occurs at a pressure much higher than “max”.

Would like to add a data point to the A5 not wanting to chamber phenomenon. I just picked up a brand new A5 built lower that had noticeably more resistance to charging and grittiness than my other 2. I pulled the spring and buffer and lightly coated Slip 2k grease and then EWL 30 on the spring, buffer and as far inside the tube as I could get. After running it manually a dozen times, it became much easier and smoother to run the charging handle.

I wonder if some of the difficulties people have had are related to this. FWIW.

[Wake27]

Just went through all of the brass I picked up from yesterday. Without counting, I’m guessing it was about 75% of all the ammo I shot but it was across a lot of different uppers and lowers. Two MEN casings had their primers blown out. One of those was the photo I posted yesterday where the primer was still there but barely hanging on. I also had two odd looking casings from some S&B 77gr that I was testing out.



The firing pin indent on those primers is noticeable more black than any of the other brass I have. The one on the right is also noticeably raised.

I just sent an update to Criterion, at this point I’m ready for them to take the whole upper and hopefully replace the barrel. I wasn’t planning on putting an E-BCG in this one so while I know it’s likely an upgrade over the REBCG, that was an extra $500 because the upper wasn’t performing how it should. I also have a ton of money invested into the optics for this gun that will just be a paperweight until this is sorted out. Or I’m playing more musical chairs with optics but I’m over that.


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[Wake27]

For your feeding problem, check your feed ramps for a burr using a Q-Tip. Even good barrel manufacturers fail to catch this sometimes, and it kinda grabs the bullet as it goes up the ramp. Just slip some cotton in and around the lug passage on the feed ramps and see if it pulls.

If that’s not it, its the A5H3. 17k and I have noticed this failure to chamber the first round problem with the A5, and for me it seems more common in the heavier ones. He solved it by removing the bias spring in his, but then reverted to a regular setup. I mostly solved it, unintentionally, by using a lighter buffer, and it only does it when I’m not trying to reproduce the problem.

The popped primers are a pressure problem, and it does not appear that swapping buffers or carriers will fix it. Your chrono results confirm this. Be aware that popped primers only occur after the point of plastic deformation of the case head is overcome by pressure, and occurs at a pressure much higher than “max”.

Would like to add a data point to the A5 not wanting to chamber phenomenon. I just picked up a brand new A5 built lower that had noticeably more resistance to charging and grittiness than my other 2. I pulled the spring and buffer and lightly coated Slip 2k grease and then EWL 30 on the spring, buffer and as far inside the tube as I could get. After running it manually a dozen times, it became much easier and smoother to run the charging handle.

I wonder if some of the difficulties people have had are related to this. FWIW.

I’ll have to remember to swab the feed ramps when I get home later.

For the A5, the two lowers I’ve been using this on have been tested pretty well and haven’t had issues. One is the most heavily used lower I own and has seen thousands of rounds across multiple 14.5 uppers. The other is newer but was my first SBR lower and so it’s seen at least 1,500 rounds across a DD MK18, Triarc 10.5, and Hodge 12.5 uppers. I don’t remember ever using anything other than A5H3s in either except for the few mags where I was testing the A5H1 recently.

Now all of that said, I do have another new lower that’s had feeding issues with a BCM MK2 14.5. It’s very intermittent but I put the Geissele REBCG in it to see if that helps. The 12.5 has not been on this lower and it does have the A5 system as well but that’s one of my most proven components at this point so I’m unlikely to expect it as the problem for now.


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[sinister]

I goggled the description of your Criterion Core barrel and it comes back Wylde-chambered vice 5.56mm (with the GI throat).

Given it looks like the German MEN ammo may be loaded to CIP or military pressures, I'm wondering if using one of Ned Christiansen's 5.56mm reamers to get you the longer military free-bore might help.

[Wake27]

I goggled the description of your Criterion barrel and it comes back Wylde-chambered vice 5.56mm (with the GI throat).

Given it looks like the German MEN ammo may be loaded to CIP or military pressures, I'm wondering if using one of Ned Christiansen's 5.56mm reamers to get you the longer military free-bore might help.

Yeah it is the only Wylde barrel I have. I know some prefer them but I honestly don’t care about that aspect, I bought it for the barrel profile, gas port size, and reported accuracy from several end users. You already noted the gas blowback in their video and while I thought the .068 was a pretty reasonable size, I did go back to find the current Hodge “large” ports are at 0.0645 so significantly smaller. I’m hoping that it is just an incorrect chamber because I know there are other much larger 12.5s out there but if Criterion won’t take care of it, I have no desire to go through that mess. I’d be more likely to just sell it for a loss with the disclaimer and replace it with a 14.5 Geissele while I wait for them to release a good 12.5 or KAC to come out with their 13.7 and CQB PRT can. I’m not sold on the SLR rail anyways. My BCM rail panels keep peeling off which has never happened on any other rail so I’m thinking their MLOK slots might be a bit over sized.

The good range near me is a four hour round trip so I don’t get to shoot enough to want to spend time dealing with all of this.


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[1168]

Yes, its a Wylde, but I have not had this problem with my 12.5” Core (yet), or any other Wylde.

[One More Time]

As I understand it, the .223 Wylde chamber is based off of 5.56 NATO chamber prints.
Freebore diameter was changed to 0.224" for a better bullet seal, excess freebore was later found to be favorable to 69gr mag length and 80 gr single fed rounds.

[Wake27]

Finally got the upper shipped back to Criterion this morning. They sent me a prepaid UPS label within a day of me sending the last update with the blown primers after switching to an EBCG but I just hadn’t gotten around to getting it in the mail. The CS rep has been super responsive so I’m optimistic about them taking care of this.


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