Actually, the problem is probably the rails on each side where the bolt rides.I usually will polish the tops of those rails and the underside of the bolt lugs (where they contact the rails).Also, work the bolt SLOWLY and note it's position when it feels rough. One last thing- BE CAREFUL!!!! The rule to live by when it comes to polishing,sanding,grinding,or otherwise modifying metal parts--- It's easier to take a little more off, than to put it back on!!!!!
A large part of the problem also comes from the magazine follower dragging across the bottom of the bolt as it is being cycled. You'll probably notice that there is a rough/hard spot right as the bolt head goes across the rear of the magazine follower. About the only thing to help this problem is to keep some oil on the contact areas. You can also start performing modifications to hold the magazine follower down a few thousandths at the rear; but if you do it too much, it may not feed properly.
I'll usually start out with 320 or 600 grit wet/dry sand paper (for the rough areas only) . I would NOT go any coarser on a bolt,(because it SHOULD be pretty much finished,and we don't want to scratch it).BUT, if the bolt, and or guides, are allready smooth,(no damage,just in need of polishing),I use a Dremel with a dense pad and rubbing or polishing compound. Don't think that because it's just a pad, that it can't damage the surface, but it is lot's more forgiving than sand paper,files,etc. Just take it slow and use some common sense,and don't get impatient. If you've NEVER done this type of thing, I'd suggest practicing on a piece of scrap metal,or somthing to get the "feel" of it. There are several other tools an procedures that can be used, ie., pencil erasers, polishing stones,soft polishing pads,etc. I'm just giving information about the way I like to do the job.
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