blown primers running 14.5 w/ suppressor

[texas12]

This weekend i was running a 14.5 DI carbine length gas system with a surefire FA556 suppressor and at least once a mag experienced a blown primer (Top hatted primer). I though ammo problem first but i experienced issues with 55gr PMC, Lake City M855, IMI M855, Hornady 75gr and black hills 77 gr. When i removed the suppressor the problem was not occurring at the same rate. I'm thinking over pressure but thats as far as I've gotten. Any thoughts would be appreciated.

[skyugo]

first time running that suppressor?
I'd contact surefire about it...

[Failure2Stop]

I would be suspicious about chamber dimension.
Sound to me like you have something a bit tighter than a 5.56 Nato chamber.

[texas12]

first time running that suppressor?
I'd contact surefire about it...

I thought it might be the suppressor so i put on a buddys gun and no issues.

I would be suspicious about chamber dimension.
Sound to me like you have something a bit tighter than a 5.56 Nato chamber.

Barrel is marked 5.56 and i have not had any issues with military 5.56 loads in the past. do you think the suppressor (and added pressure) just inflamed an existing problem?

[Failure2Stop]

Barrel is marked 5.56 and i have not had any issues with military 5.56 loads in the past. do you think the suppressor (and added pressure) just inflamed an existing problem?

I think that the increased fouling in the throat/lead might be exascerbating the issue, and if removing the suppressor made the issue go away I am inclined to believe that it is doind something else as well, though it is a bit counter-intuitive as far as operation goes.
Who is the manufacturer of the barrel? Not all 5.56 marked barrels are actually 5.56 dimension chambers.

[BufordTJustice]

I would be suspicious about chamber dimension.
Sound to me like you have something a bit tighter than a 5.56 Nato chamber.

+1. If it's with multiple dif types of ammo, I'd explore the chamber dimensions a little more.

You may want to look for a 5.56NATO chamber reamer by Ned Christiansen at Michiguns. A "5.56 NATO" stamp on the barrel does not always mean a 5.56 NATO chamber, unfortunately. Certain manufacturers have been known to stamp the barrel as 5.56 NATO, but when a chamber reamer was applied, MUCH material was removed.

A 5.56 NATO chamber reamer should basically spin freely if your chamber is already within 5.56 NATO dimensions. If you have closer to a .223 SAAMI chamber, it will drag and you'll feel it.

[texas12]

I think that the increased fouling in the throat/lead might be exascerbating the issue, and if removing the suppressor made the issue go away I am inclined to believe that it is doind something else as well, though it is a bit counter-intuitive as far as operation goes.
Who is the manufacturer of the barrel? Not all 5.56 marked barrels are actually 5.56 dimension chambers.

It is a goverment profile CMMG with .750 low pro gas block. I have also expecienced more then usally malfunctions in the last month as well. Just not to this extent.

[Failure2Stop]

When is the last time you thoroughly cleaned the chamber and bore?
How often (round count) do you normally clean the chamber and bore?
What issues have you seen recently?
I have heard reports of CMMG guns with tight chambers, so it is possible that you are seeing these issues popping up recently due to accumulated fouling in the throat/leade.
I am not saying that this is definately the issue, just trying to help diagnose if this might be a problem, because a good scrubbing is a lot cheaper than any other fix I know.
You might want to have your chamber hit by Ned Christiansen's 5.56 reamer, but if no one in your area has one you can borrow or rent or have a gunsmiff use, it is kinda cost-prohibitive.

[jsebens]

I have personally owned a CMMG gun marked as 5.56NATO that was not. Thanks to them, I spent the better part of a 3-day rifle class shooting a handgun instead...I should probably thank them for all the transition practice. As has been suggested, check the chamber.

[texas12]

When is the last time you thoroughly cleaned the chamber and bore?

about two weeks ago i did a thoroughly clean and used a parts washer too.

How often (round count) do you normally clean the chamber and bore?

any time i shoot the gun I clean it and usally thoroughly.

What issues have you seen recently?
I have heard reports of CMMG guns with tight chambers, so it is possible that you are seeing these issues popping up recently due to accumulated fouling in the throat/leade.

I have experienced failure to eject a few times, were the spent casing is very tight and i had to hit my stock against the ground to get the round out. I have also experienced failure to eject were the bolt ripped the rim of the casing. I'm starting to think the chamber is the problem.

I am not saying that this is definately the issue, just trying to help diagnose if this might be a problem, because a good scrubbing is a lot cheaper than any other fix I know.
You might want to have your chamber hit by Ned Christiansen's 5.56 reamer, but if no one in your area has one you can borrow or rent or have a gunsmiff use, it is kinda cost-prohibitive.

The chamber does not seem like its fouled up. Is it possible its time for a new barrel?