MKII Bolt smoothing

I have 2x MK II Youth rifles, my kids first rifles. One left hand, one right hand bolt. I noticed on the left hand that the bolt isn't anywhere near as smooth as the right. I pulled the bolts out and saw that where the serial number is etched is nearly smooth on the right hand bolt but is pretty rough on the left hand. Would this contribute to a rougher bolt throw?

Interestingly enough, my 17HMR bolt (similar but different length it looks) doesn't have the number etched on this same area. I can provide pictures if it would help.

So to sum it up. I have 3 similar bolt actions. From smoothest to roughest I have, no number etched on bottom of bolt, a smoother etching, and a rougher etching.

I've seen info on polishing bolts online, but none of it touches on this area. I don't really want to rip the bolts apart if I don't have to.

Thoughts?

If the action screws are too tight it will make the bolt bind. Due to the lack of bedding area in the stock, over tightening the screws will actually bend the receiver.