TulAmmo .223Rem Fail

Tula "White Box" 55 grain, and Tula "Black Box" 55 grain .223 Remington

I bought 5 boxes of 20 rounds of Tula "White Box" .223 Remington at a gun show a few months ago and shot them through my 16" LMT M4, tax stamp LMT 10.5", and Bushmaster ACR.  Those, I had no problems with.  So, I purchased a 500 round spam can of TulAmmo "Black Box" .223 Remington sealed up in a "spam can."  Working the coupons and deals for The Sportsmans's Guide, I got a pretty good price on the can.

Today I took a bagful of loaded mags, and the 10.5" LMT and the ACR, out to the indoor range.  I put a few mags through the ACR, including a couple mags of Tula, with no issues before switching over to the LMT shorty.  I loaded up the LMT with a Troy Battlemag full of Tula, dropped the bolt, and flipped off the safety.  BANG!  Dead trigger.  After the first round, the bolt came back and ejected the steel case, pushed the next round maybe a half inch, and stopped.  I thought that was weird, because I had no problem with the "White Box" ammo.  I haven't run the Troy mags much, so I grabbed a PMag full of Tula.  The exact same thing happened.  I pulled back the bolt, and let it fly, chambering a round.  BANG!  Dead trigger.  Short-stroking.

Fortunately, I had brought a couple mags full of PMC Bronze .223 to try, and I had a few mags of my almost 5.56mm NATO spec ammo to shoot through the LMT, and the ACR chewed through the mags full of Tula.  Although I keep a few different recoil buffers in the rifle bag, the one in the LMT 10.5" carbine was already a standard carbine buffer, and I don't have anything lighter, if there even is anything lighter.

I know the problem isn't the steel-cases.  They are Boxer-primed, and I've reloaded hundreds of Wolf and Tula steel-cases and run the reloads through the same LMT without issue.  My loads were approaching 5.56mm NATO pressures though.

So, the ACR is proving to be capable of digesting anything I can fit into the magazines.  But what does it say about the Tula ammo?  Did I get a "vodka special" batch?  The "White Box" ammo, and the "Black Box" ammo should be the same, but obviously what I got wasn't the same.  I suppose this would explain the mixed reviews on Tula ammo.  Luck of the draw?  You get what you pay for, perhaps?

White Box Manufactured: 07/09 (I'm not sure if that's European for September, 2007, or if it's July, 2009)
Lot: 7Q5 4

I think this is the lot for the Black Box ammo, but I don't know how to read it.