Hi, I have an A1 rear sight and I would like to drill the close range hole at the same diameter as the A2 sight. Is anyone could tell me the holes diameter on A2 sight.

Thanks,
Clovis

Somebody should know that???

I think you are better off substituting the A1 rear sight peep with an A2.  When we made this change in 1983, we left the thread pitch of the windage screws the same, so one could do exactly what you want, without lossing the shorter range peep of the A1.
If you still want to drill it out, its diameter is 5mm.  Same as the Viet-Nam era LLL sight kit.
But since you will be disasembling the rear peep out of the carrying handle in order to hold it properly in a drill press, why not just substitute peeps?
Not planing to disassemble and use a drill press?  Then you want to enlarge the peep a little bit at a time using the next drill size up in your set until you reach 5mm.
You might also wish to test fire at 3.5 or 4mm to see if that's ok for you.

Thank you Coldblue for all the info. I was not sure if the threads were the same between the 2. Since they are I will probably order a new rear sight.

Have a nice day,
Clovis