Blown primer...what next?

[nightchief]

Not really sure which sub forum this belongs in...mods, please move if needed.

On Monday (July 3), I was running my SBR suppressed when it locked itself up tight. Bolt Carrier was unmovable half way into the RE and half way into the upper receiver. To get the BCG loose, I ended up removing the RE and knocking the bcg forward softly when a primer dislodged itself. This fixed the malfunction, but now I have concerns about the over pressure that occurred and what may need to be tweaked to avoid this happening going forward. It's possible it was a one off issue with one bad cartridge, but I have had a few issues running this particular cartridge with this set up. The intent with the rifle was for it be usable for HD, but this latest issue has me regulating this upper to range use only. Its kind of expensive for a range toy. I've got probably 600ish un-suppressed rounds fired using a wide variety of ammo and no issues since some initial fit trouble causing FTF's.

Set up is 11.5 CL barrel with .070 gas port, carbine gas system; non adjustable gas block; mil-spec carrier; A5 RE with A5H2 buffer; Surefire 556-212 suppressor. This occurred using IMI M193 from an Okay 30 rd magazine.

I would like to be able to reliably shoot 556 77gr OTM type ammo suppressed. I would also prefer not to use an adjustable gas block. Looking for advice on what adjustments to make now. H3/H4 buffer? Different carrier (like LMT-E or Gemtech adjustable)?

NC

[Colnago]

As I think about your description of events, it seems like blowing primers is unusual for this rifle which makes me think it is over charged ammo that is causing your malfunctions. You said you had other problems with this batch of ammo as well. I got a bad batch of IMI ammo recently that blew primers and caused my KAC to lock up in a similar way to what you describe. I sent it back and the gun functions smoothly with a wide variety of good factory ammo and hand loads. I shot it 4 or 5 times with no issues before my confidence in the gun for HD applications was regained.

[markm]

Gas port can be removed from the conversation. You're good there. I'd bet the ammo is to blame. I'd try black hills 77s in both 556 and 223 loads.

There is an outside chance your chamber needs reaming. But I think it's the ammo.

[Clint]

Has all the brass been inspected for blown/loose primers?

Odd are low that ONE primer will lock up the gun. Most likely several came out and one got lucky.

Where did the primer get stuck?

[nightchief]

Has all the brass been inspected for blown/loose primers?

Odd are low that ONE primer will lock up the gun. Most likely several came out and one got lucky.

Where did the primer get stuck?

I checked all the cases I could find, and never found any with a missing primer. Primer was lodged between the carrier and upper receiver somewhere. Carrier was stuck to the point of needing to tap it out with a mallet...when it came loose, the crushed primer fell on the ground, so I'm not sure exactly where it was lodged. Some additional info, outside temp was about 95 degrees, and I had run two, 20 round mags through it suppressed. No mag dumps, but with some multi round, high speed shots. I had run quite a bit of GECO 223 and PMC bronze before hand with no issue. When I went to the IMI 556, this occurred on the 2nd or 3rd round after changing mags.

[nightchief]

Gas port can be removed from the conversation. You're good there. I'd bet the ammo is to blame. I'd try black hills 77s in both 556 and 223 loads.

There is an outside chance your chamber needs reaming. But I think it's the ammo.

That was the supposed to be the next ammo to run after the IMI, when the gun locked up. I will definitely try the BH 77 gr next. Perhaps some Fed Gold Metal Match 77gr SMK too.

[Iraqgunz]

It can happen, the question is whether or not it's happening more than once. I would try other ammo just to make sure it's not something else.

[markm]

Odd are low that ONE primer will lock up the gun. Most likely several came out and one got lucky.

I'd guess that half of the primers I've had blown in our ARs will end up in a really shitty spot. The have a magic way of getting into the worst possible places.

[Spin Drift]

Had one end up in the FCG, turned an SR-15 into a Jam-O-Matic, had to bust open the lower(push pins and trigger/hammer/selector…) to get the primer out, wasn't visible.

[vicious_cb]

I'd guess that half of the primers I've had blown in our ARs will end up in a really shitty spot. The have a magic way of getting into the worst possible places.

Blown primers, even a single one are magnetically attracted to the fire control group. It's one of the laws of physics or something.