You need to determine what you have. Those in the know will need to see the head stamp, and or the packaging and they can tell very accurately what you have and tell you if it's corrosive. You could possibly have some that is and some that is not unless you verify it's all the same.
What is the head stamp? If it is US manufactured stuff there will be a year and a plant ID. The year is just 2 digits like 42 or 53 for 1942 or 1953 etc.
If your ammo has a pre 60 date then the primers are probably corrosive. Good news is just clean your barrel and chamber well after shooting the stuff and you won't have any problems. Still a lot of 03' Springfields and Garands out there that have shot lots of corrosive ammo and yet still have great bores as a result of proper care.
They become "corrosive" when they are fired. Just clean your barrel well after shooting it. I used to use a wet/damp (water) patch or two and then clean as usual with solvents, brushes and patches. Light oil and you are good to go. The brass should be reloadable, but I'd deprime and tumble it within a short time after firing it, making sure to clean the primer pockets well.
DO NOT just give the bore a good cleaning after shooting ammo with corrosive primers. The normal oil based solvents, like Hoppe's, will not wash away the corrosive salts left after shooting.
The way I did it when I shot ammo with corrosive primers is after the last shot, while the barrel is still hot, run a few patches through the bore soaked with Windex, yep, plain old Windex.
I don't know if its the ammonia in the Windex, or just the liquid that washes away the salts, but I guarantee it works.
Here's a handy way to test whether the primers are corrosive:
Take a cartridge, and with a bullet puller, pull the bullet and empty the powder out.
Take a plain, steel finishing nail, and some sandpaper, sand it down to shiny bare metal, and clean it off with some alcohol to make sure all oils are gone from the surface.
Place the nail in the empty cartridge, chamber the cartridge, and pull the trigger to ignite the primer (pointing up, of course, so the nail doesn't fall out.) And no, the nail will NOT come flying out the muzzle. Wear ear plugs, the primer will be loud.
Unload the cartridge, and, without touching it with your fingers, pull the nail out of the cartridge. Use pliers or something.
Then, still not touching the nail, nail it to your workbench in your garage.
Look at it the next day (it shouldn't take but over night.)
What does the S L 3 5 represent?---What is the best way to pull the bullet--I don't have a bullet remover---Sorry,I am a shotgun guy but do have 30-06 for hunting and had this stuff around for yrs and would like to shoot it off without any damage to my gun---ThanksSJB---
SL 35 is corrosive ammo. SL stands for Saint Louis, that's where it was made. The 35 stands for 1935, the year it was manufactured. Timb99 is right, normal cleaning does not work. Only the primer is corrosive, the bullet, powder and case are good. HMB
Old military ammo with Mercuric primers is corrosive but with proper cleaning methods will not cause any problems. As a member of the British Army I shot many thousands of rounds through the Lee Enfield with no problems. Standard procedure was to flush barrel with hot water the pull through patches until clean then pull through with oily patch, In combat situations when no hot water was available we pissed through the barrel and it worked. Maurice ( The Brit. )