Was looking to pick up a couple of spare extractors and came across some that were described as "Extractor Produced from MIL-S-5000 Steel, Vacuum Hardened, Machined." I then searched for "MIL-S-5000 Steel" and found, in general, that is seems to be the same as 4340 steel. Does anyone here have any background or knowledge of MIL-S-5000 Steel?