How can you tell if SKS ammo is corrosive?

Pepperpopper

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So obviously when buying 7.62x39 ammo the supplier may say which the ammo is, but I have been in hardwares where the ammo is sold by people with little knowledge. Is there any way of looking at the crates and telling. Is it primer specific, on non-corrosive always says it is?
 
Pull a bullet and dump the powder. Fire the primer only cartridge onto a non-stainless steel drywall knife (wear eye protection just in case). After a few days if the powder residue has rusted the steel on the drywall knife then your ammo is corrosive.

I have used this method in the past - if anyone has a better test I'm always happy to learn.
 
Chinese ammo in the green wooden crates with 2 zinc spam ammo is highly corrosive. It left a covering of orange rust on my piston after just one day.
 
Chinese ammo in the green wooden crates with 2 zinc spam ammo is highly corrosive. It left a covering of orange rust on my piston after just one day.

Highly? Lol! It either is or isn't.
What you experienced was nothing short of accurate for leaving the rifle uncleaned afterwards for a whole day.
 
For the nail test, pull the bullet and dump the powder. Take a standard steel nail, sand the surface to remove any anti-rust coatings then tack it into a piece of wood. Place the now empty casing over the nail and ensure the case neck contacts the wood so the entire nail is enclosed. Place the bolt from your sks over the base of the cartridge. Wear ear and eye protection then strike the back of the firing pin with a hammer. Leave the casing over the nail for at least 1 day. After several days you will start to notice the corrosion on the nail. If after a week it is just black, then it is non-corrosive. If it looks like an old cast iron pipe left in the ground for 20 years, covered with rust then the primer is corrosive.
 
Nail test is only necessary if you have loose cartridges of unknown origin.

If it's in a crate or can, its corrosive surplus.
 
Not always. Theres old chinese 7.62x39 lead core non corrosive that came in crates.

I have some of that I purchased a few years ago from CanAm and from Frontier. I have confirmed personally the rounds I fired from those Chinese spam-cans as non-corrosive including headstamp "72", btw they came in wood coloured crate (not green crate) silver spam-can (not green can), individual ammo casings are green.
I keep hearing people saying there are chances there are corrosive mixed in the same non-corrosive spam-can, and the suggestion is that nail test is the only way to tell, not by reading the headstamp alone.
There lies the logical problem, if the same spam-can is possible to have some corrosive in it potentially, there is no logical way to nail test each round before firing it. Is that the reason why people insist on treating the whole spam-can as corrosive?
 
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The long and short of it is, if it is military surplus from a former soviet country, russia, poland, czech, etc, it is corrosive.

If it is military surplus Chinese from before around 1995, it is corrosive (middle number on crate, ex 31-71-13 is made in 1971). The 1971-1973 chinese in green crates has been sold and labeled at "non corrosive" but i have found that not to be entirely true. I had one spam can that the first 300ish rounds were non corrosive, didn't clean my sks, never had any problems, the last 100-150 rounds rusted everything it touched. So even if you do the nail test on this early 70's ammo, it's not consistent. You would literally have to test every round, but then you would get to shoot any of it. My guess is they were experimenting with non corrosive primers around this time, but it wasn't consistently applied across the board.

If it is chinese surplus made after or around 1995 is may or may not be corrosive and you will need to test to make sure.

If is comes in 20 round boxes with big bold letters saying "NON CORROSIVE" then it is likely non corrosive.
 
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