Originally Posted by jack404
I've found drills not the best tool for "dinged " chambers , where there is metal one side a drill will try to self centre between that and whats opposite and that means a distorted chamber ,
dings are best removed with a file , and while the result may not be perfect only one side is off and you can get it just about perfect by eye with practice and a hard sharp file , if you can mount it in a lathe and do it that way , more's the better really ..
when doing new chambers yeah a number 1 wire size drill is what i use , but thats when everything is equal to begin with
Jack, if you re-read the OP's post he's using the shank of a #1 drill bit with a flat polished on one side. He's not drilling with the bit, just using the shank as a mandrel (or chamber iron).
I've never done this with a .22lr chamber but I know it can be done. IIRC, this homemade tool idea is in one of the Brownell's Kinks books too.
I have made several of basically the same tool for raising dented shotgun muzzles. Works good on shotgun barrels, should work to iron out a rimfire pin dent too.