Hi All,
I've got a SR-556 that is blowing primers and mauling the case head of a particular brand of ammo.  The ammo in question is brass cased, 55 Gr FMJ.  It seems the Ruger doesn't like this brand but will function everything else.  The ammo in question works in my Palmetto and Stag (DGI guns) with no problems (no blown primers or mauling of the case head).  I've tried adjusting the gas piston from setting 2 to setting 1, to see if the rifle was over-gassed, and it didn't make a difference.  The Ruger is blowing primers out of this ammo about 4 out of 5 rounds.  

So here's the questions.
Has anyone else had a problem with their Ruger with certain brands of ammo (blown primers/mauled case heads)?
Is this a problem with the rifle or the ammo (I would lean toward the ammo since it works in the other rifles)?

If it's the ammo, it will be relegated to use in my bolt rifle.

Thanks,

Sounds like over pressured ammo?

I would go with ammo problems too. Most likely your Rugers chamber is tighter, so the problem is more obvious. And changing the gas setting will not make a difference since that only affects the gas sent into the piston to cycle the action.

My SR 556 has never blown a primer with any type of 556/223 ammunition. My vote is the ammunition is the problem.

How does other ammo work in gthe gun?  Is this the only ammo that does this?  What brand and or type (#) ammo are you using?

This is the only ammo that doesn't function in the Ruger.  The ammo functions fine in my other AR's.  The ammo in question is the blue box Independence AR5.56.

As I stated earlier (scroll up a bit), that it does not blow out the primer in other AR's does not mean it is any good...