You're looking for "Perma-Slik G" which is the Mil Spec. moly coat found on USGI Mags. Says so on the can.
Do a search on "Perma-Slik G" and you'll find the source.
Method of use:
1. Disassemble, Clean, Degrease with Simple Green and dry.
2. Lightly sand mag body with "Fine" sand paper. I like to use the Foeam Sanding Blocks. Lightly sand floor plate.
3. Suspend mag. by hooking from ceiling with close hanger through the mag catch hole, or use a plastic coat hanger slid into the bottom of the mag body as a "Holder" while spraying.
4. Lightly spray on 1 coat.
5. Let dry to touch and lay on paper towel covered cookie sheet and bake in oven at 200 degrees for 30 minutes. (No it won't screw up the oven!)
6.Repeat #4 an #5
7. Let cool.
8. Lightly spray floor plate with "Flat Black" Rustoleum spray paint. 1 coat will do. Let dry overnight.
9. Reassemble
10. To remove "Powder Coat" (which will rub off pretty quick anyway. It's really just overspray.), rub the mag body down with a cotton rag impregnated with a light lubricant like 3 in 1 oil, or WD-40.
That's it! Remember that the magazine was designed to be a "Disposable" device. Therefore the original moly coat is not "Bullet Proof". You will see wear at the mag catch hole after a few insertion and extractions of the mag.
This is great fun and you can actuallyt make some fairly good profits if you buy the "Very Used" USGI mags for under $10.00. Refurbished mags go for around $20.00 to $25.00 each for 30 rounders. More for 20 rounders.
Hope this helps.