Headed out to the range this morning to make loud noises.
I was just starting with my FAL, thinking how sorry I was for the boltgunners on the line because my muzzle brake was going to deafen them.  
I had just discovered earlier that I did indeed have the capability to shoot fairly accurately with both eyes open.
Lined up on the target without shutting an eye, and squoze the trigger.
It was a muffled whomp, not a howitzer-esque BOOM.
First thought: That wasn't too bad.
Second thought: That wasn't too bad because something is wrong here.
'Bout that time I realize I just got a faceful of hot gasses and my receiver is smoking out of every hole and seam.
Line went cold immediately because everybody heard what I did, and one girl actually saw it happen.
RO came over and asked what happened and I showed him the magazine, which was missing a floorplate and was ballooned out near the bottom.  "Probably a case rupture", he said, , and said he could take the ammo to examine how bad the batch was/had gone (it was Chilean milsurp which I had bought two years ago; I had shot 250 rounds out of the 500 round batch on prior trips).  We found the dented primer on the bench, but didn't find where the case had gone.
Three people looked in my bore, commented that it was the cleanest FAL bore they'd ever seen, and saw no ring where the barrel would be bulging.  I don't figure there was an obstruction.
I decided to pack it up and head home while I was still ahead.  Found out the Longhorns lost, and I now owe ilikelegs a 30 round AR magazine.  Crap

Quoted: Perhaps you had a stuck firing pin and it was an oob.

I considered that.  Consensus was uncertain.

Quoted: First, be thankful that you weren't heard. Second, find the cause and make sure it does not happen again.  I don't know much about Chilean ammo - what is the reputation of that stuff?

I am thankful.
I don't know about the reputation of Chilean.  ETA - I don't have any more Chilean.  Richard (the RO) has it now.

i shot a bit of that chilean stuff a couple of years ago. Kida iffy ammo at best. poorly stored and poorly made. i got rid of the little i had. i consider on par with the idian crap floating around today.

mike