I recently had a squib with some of my XM855PD.  I had a pop but nothing happened so I stopped and checked the brass as I extracted it.  No bullet.  I looked down the barrel, and could see the base of the bullet at the front of the chamber.  NO OTHER ROUNDS WERE FIRED.  Took it home and used an old cleaning rod to remove the round from the bore.  I noticed that my barrel nut was loose, and that if I held the upper recever, and wiggled the FSB, the barrel nut and barrel would twist a little.  I removed my handgaurds, gas tube and re tightened the barrel nut, not having seen anything amiss.  My question is do you guys think the two are related, and is there any concern about the barrel?  It is an MOS 1-7 twist Chrome lined barrel.

I don't see how a loose barrel nut could cause a squib load. Charles the Gunsmith.  

Like Charles said I don’t think the two are related, but……..the squib load was probably a sign from the AR Gods which lead you to the discovery of the loose barrel nut!

A squib load comes from a round with very little or NO powder in it.  The primer alone is strong enough to start the round down the barrel.  I don't see how one has anything to do with the other.  Good thing it happened or you would not know the barrel nut was loose.

MadDog

My question is do you guys think the two are related, and is there any concern about the barrel?

 Nope.

Quoted: I recently had a squib with some of my XM855PD.  I had a pop but nothing happened so I stopped and checked the brass as I extracted it.  No bullet.  I looked down the barrel, and could see the base of the bullet at the front of the chamber.  NO OTHER ROUNDS WERE FIRED.  Took it home and used an old cleaning rod to remove the round from the bore.  I noticed that my barrel nut was loose, and that if I held the upper recever, and wiggled the FSB, the barrel nut and barrel would twist a little.  I removed my handgaurds, gas tube and re tightened the barrel nut, not having seen anything amiss.  My question is do you guys think the two are related, and is there any concern about the barrel?  It is an MOS 1-7 twist Chrome lined barrel.

I had the exact same thing happen with XM193PD recently.  It is purely an ammo issue - the casing probably had little (if any) powder in it.

I've decided to not use PD ammo any longer - because I already sorted them by hand, and the time spent doing that isn't worth the money saved - expecially not with the risk of a squib.