Hey y’all pulled my bolt out to change gas rings and inspect bolt . Seemed a bit sloppy last few times I cleaned it so figured it was about time. When cleaning I noticed some strange finish wear that I’ve never noticed before. Looks and feels like etching . Kind  of raised almost like rust but it’s not rust. Doesn’t come off with nylon, copper or steel brush and hoppes . I have a couple replacement bolts and figured I’d swap it out for a new one until I hear back from someone here. It’s a toolcraft 9310 parked. At around 5-6k round and has been through periods of neglect ie 1-2000 rounds between cleaning . Using 10w30 and or high temp bearing grease for lube. Let me know what y’all think About the wear and whether I should swap it out. Thanks.

Corrosion. I'd run it and just keep an eye on it if a range gun.



If it's in a life/death gun replace it for peace of mind.

Corrosion from neglect.

If only something like PMCS existed.

Right on, thanks for the feedback  . I’ll keep it as a spare. I’m assuming PMCS means preventative maintenance? Been cleaning my guns after every range trip again for the last year or so. I guess I shouldn’t have listened to YouTube people. Y’all have any input on why it only happened to the bolt and not any of the other parked parts? Extractor, carrier, barrel and lower parts still look fine.

Not often but shows up on some bolts after firing. Sometimes just a few rounds. always figured it was caused by incorrect atmosphere in the treatment oven.

Glad to know I’m not the only one. Thanks

Sadly, I have a Knights bolt in a KAC M4 upper that is corroded/pitted like that

Corrosion of the 9310 steel.

I've got a few spots on my 6720 extractor from after just a few rounds.

Conditions were right ( or wrong) for that particular alloy for corrosion, even the type of residue from the burnt powder could contribute to the problem. Can be non-consequential most of the time, but maybe a combination of temperature, humidity or other unknowns came together.

Have seen that in other industries for replacement parts with identical specs, but different lot numbers. One part lasts in a harsh environment aside from the expected wear due to use. An identical spec part right next to it needing replaced due to excessive early corrosion.

I'm doubting that this is corrosion. Instead I think this is how it looked out of the factory and only reason you noticed it now is because it gotten dry.

I have a couple of DPMS bolts that have similar appearances. After putting some oil, it looks okay for a while until it drys out then it looks like this again. Other bolts in the same bin, such as BCM do not show this when dry.