Here's another possibility.
Did you possibly get a cartridge that had a much heavier bullet than was listed on the box?
The machines should be set up to kick out any upside down projectiles and any that are too long.
If the wrong profile piece was installed, then a heavy/long bullet could pass through the kick out tab and get loaded.
Not only would the powder charge be wrong, but the heavier/longer bullet would be much, much deeper in the case causing pressure to skyrocket.
Let me give you a personal example:
Loading 17 Hornet with a 20 gr V- Max, WSR and AA-1680.
Known safe load.
I resize my brass, add the primer, charge with powder and grab a box of bullets.
Load them up and hit the range the next day.
The bullets are shooting great, but impacting about an inch higher than they should.
Hmmm...
The third round of the second group I feel a little puff on my face. Rifle is a CZ 527.
I eject the cartridge and notice a little primer leakage. Not normal, but I figured I might have had a bad piece of brass.
I proceed to shoot a couple more groups without incident (or so I thought).
When I picked up the brass 3 or 4 had completely blown primers to the point they fell out.
I was done for the day.
The 17 HH is designed to operate at 50ksi.
We'll come back to this in a bit.
The 223 is listed at 55ksi and 5.56 is 58ksi.
CIP lists both at 62ksi.
Either way, even if the cartridge had been a 5.56 loaded to 58ksi (SAAMI) and fired in a 223 chamber, it would most likely not exceed 65-68ksi.
To do the damage it did to that piece of brass, it had to exceed 75-80ksi to even come close to that.
Most likely, the pressure exceeded 80ksi.
In my above example in the 17 Hornet, the cause was easy to diagnose.
I simply grabbed the wrong box of bullets that should not have been in that stack.
Instead of loading 20gr bullets, I loaded 25gr bullets.
Okay, 5 grains, so what?
In a 223, 5 grains will get you some primer flattening and not much else. Really, it's less than a 10% weight increase. Not good, but not dangerous.
Let's go back to the 17 Hornet.
What does 5 grains mean?
First of all we're dealing with a much smaller bore so any increase of powder gives huge increases in pressure and velocity. The max charge is like 12.2gr.
Now let's up the bullet weight 25% and go from a boat tail to a flat base that also increases bearing surface.
Bad, bad, very bad combination.
My 50ksi cartridge just became 65-70ksi and blew a couple of pockets.
Could the issue with your Berger ammo be as simple as a few extra heavy bullets ended up where they don't belong and got accidentally loaded into your ammo?
Highly likely.
I used to be a production manager for an ammunition manufacturer.
Most of our employees knew their jobs well, but had no idea how dangerous a seemingly innocent gesture of picking up a few bullets off the floor and tossing them into the nearest bucket could be.
What is the probability of something like that happening?
Very high I would think.
We had a scrap bucket for anything picked up from the floor just to prevent that.
Thanks, Sherlock. I didn't post to one-up the severity of Molon's experience. Just wanted to add another point of reference.
