7.62x39 LAPUA corrosion


#1

hello
i buy two rounds of 7.62x39 LAPUA (headstamp:lapua 7.62x39) one year ago
they are in new shape or condition ,but today i find the two rounds with badly corrosion (on the neck)and neck cracked ,and the powder charge is degraded on neck aera (the bottom of casing is in the same new condition)
i would know what this corrosion ? (i ve see this on few lapua calibers but these are not my rounds)
sorry i can’t make pictures


#2

I bought a box of SAKO 8.2x57 JS with 200 gr soft point HAMMERHEAD bullets about six or seven years ago. The box was heavily shelf worn but the cartridges looked good except for one with a spot of corrosion on the neck. A few months later I opened the box and there were five or six with creeping green crud on the projectiles and the case mouth. I pulled the bullets on the corroded cases and found that there was a coating of green crud where ever the powder had been in contact with metal. In the worst couple of cases, the powder had picked up a blue green tinge from the copper corrosion. I went on to pull the remaining bullets for the whole box and every single cartridge had the same problem. My theory is that the acids had not been properly washed out or neutralized in the powder. About that time, another collector on the forum posted a question about corrosion on one round out of a box of SAKO 9.3x53R. I told him of my findings and he ended up pulling the bullets from every round in his box too. There was corrosion inside every round. Maybe there was a catch of bad powder circulating in Finland.

Curt


#3

I also have some boxes of Herter’s ammo in a couple of different calibers ammo that displayed corrosion on the soft point where the gilding metal meets the lead. Off the top of my head, I don’t know if they were made by Norma or Lapua. I have a box of Dominion 6.5×54mm Mannlicher-Schönauer that showed neck corrosion on a couple of rounds. I pulled those bullets and found the corrosion seemed to be coming fro the base of the bullets. I don’t remember if there was exposed lead or not. The two rounds in question were not matched to the other eighteen, but came from somewhere else to top up a box that was sold as full of proper rounds and “sealed” in cellophane. I guess every one here knows how much that guarantee is worth. Any way. I kind of figure that kind of corrosion is caused by residual flux or some other bonding agent. It could also be from residual sulfuric acid that is used to clean the metal.

Curt


#4

hello
thank for your response
i see also a corrosion on few rounds on a box of sako 9.3x62 hammerhead
sadly i cannot pulled the lapua and sako rounds because these bullets are very crimped on casing


#5

I have never tried it, but I heard one trick for pulling a heavily crimped bullet is to push the projectile back into the case a short distance before driving it out with a kinetic bullet puller. You might also try a penetrating oil if you think the corrosion has frozen the projectile to the case neck, but the corroded bullets, that I have pulled so far, have all extracted OK without any oil.

Curt