I have some loaded cartridges, some are marked DEN 42, which I assume were made in Denver in 1942 (almost as old as I am!) but the majority are marked STW 4. Anyone have a clue what STW 4 means?

I think I read somewhere that the WWII stuff is non-mercuric. is this true?

Thanks.

Closest I've found is ST.

https://www.cartridgecollector...age=headstampcodes#R

Mercuric primers went out in the early 1900s. But, WWII primers were/are corrosive

And TW; twin cities ammo plant in Minneapolis.

Twin Cities make sence (note the spelling, dpcd, and I'lll have you know that I made it all the way thru the FOURTH grade.).

I wonder HOW corrosive; A good cleaning after shooting will do it?

And I'm proud of you.
But my Mother was an English teacher and she would beat us for that. Back when you could beat kids.
Yes, all WW2 M2 ball is corrosive, so clean with either RBC, or water. Do not use oil, first; that will only lock the salt in the steel pores.
Have to dissolve the salts first. Then oil.

Great, thanks. Sort of like working with black powder.

Good advice Tom. Way too many rifles have been ruined by incorrect cleaning procedures. As to the "beating of kids" theory; I damnded sure didn't like it when I was a kid (I deserved it of course) but I firmly believe that it helped to build solid character. I'm not talking abuse of course but by today's standards that's what it would be classified as; mores the pity. I whipped my kids when they screwed up + made them haul rocks to build a wall + guess what? They all 3 turned out just fine with a good work ethic + living productive lives. Way too many parents can't say the same about their kids.