PMC case discoloration

zykopat

zykopat

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Hey,
just got a shipment of PMC 55gr FMJ-BT and I randomly checked some cartridges and they are all discoloured from under the shoulder up to the neck. What caused this and what does it tell us?

PA040054r.jpg


p.s. notice the Conservative Party colours chosen for the sketch
 
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No, that is where the case was annealed to ensure maximum ductility. That means you can be sure it will not crack upon firing.
 
thanks guys. I found that odd because I have Winchester USA white box 55gr. and their cases don't have this discoloration and the bullets are also annealed...
 
Bullets are not annealed, cases are. Some factory cases are tumbled after annealing, and the discoloration disappears.

Or, Winchester may be trying to hide something...........
 
Well, my understanding is that this PMC stuff is military grade, 5.56...(M193)....Apparently, the annealing at the case mouth indicates military ammo....
 
Civie ammo is supposed to be bright and shiny for marketing reasons. After annealing it is pickled in an acid wash then washed in clean water. This makes it bright. (This is how we cleaned brass at CIL in the 60's. Maybe done differntly today. But we were making over a million rounds a day, so I know pickling is well suited to volume production.)

Military ammo does not have to be pretty. I don't have any military spec sheets any more, so don't know if the spec calls for the brass to not be washed. I have been told (but it might be an urban myth) that a batch of unannealed brass once got loaded and the cases all split later, so that the military now specify the brass not be washed so it can be seen to be annealed.
Probably a myth.


I have loaded a lot of surplus virgin military primed brass in my Dillon. Every once in awhile I can hear what sounds like a bell ringing in the case feeder hopper. It is a case that missed the annealing. It is so hard it rings like a tuning fork.
 
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"...Military ammo does not have to be pretty..." Exactly. The military doesn't care one way or the other as long as the ammo is reliable and meets accuracy specs. Said accuracy specs aren't terribly accurate either. 3" at 100 for standard IVI ball 7.62, as I recall.
 
GANDERITE said:
...a batch of unannealed brass once got loaded and the cases all split later, so that the military now specify the brass not be washed so it can be seen to be annealed.
Probably a myth.
Click to expand...

Certainly it is not a myth that brass that is not annealed is much more susceptible to cracking. Annealing of brass cases was developed after the British experience in India, when Martini-Henry cartridges would split during the monsoon. I have also heard that the annealing colours are left in place on military ammo so that QC (and government inspectors) can tell at a glance that the cases have been properly annealed. It would also be silly to take the time and cost to clean it off, it is just a comsetic discolouration.
 
I should have paid more attention to some things 45 years ago - and kept all the publications that have crossed my desk..

During the Vietnam war the US Army contracted with the Canadian Arsenal for 7.62 ammo. The arsernal made their own brass, but we (CIL) were given a contract to make brass too.

We knew how to make 308 brass, but there were a lot of changes made for making the military. Obviously the cases were to be heavier and the dimensions were slightly differnt, but I do recall that the specs for annealing the case were different. The case had be be made harder so the riim would not pull off in a machine gun or semi-auto.

I cannot recall if we washed the cases. I assume not, since that would have been a waste of time and money. This might be when I was told that the contract required that cases not be washed so that there was no doubt the cases were annealed.

But, since I do not remember it might just be an urban myth that militaryc ases are not to be cleaned after annealing.
 
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