Originally Posted by shortgrass
No, it is not. The #28 or a 7/64" drill bit will just follow the existing hole. Find a competent gunsmith.
it can be done in a Bridgeport mill, but you'd better know what your doing before you even start. You use a two flute end mill that's ground to the correct diameter. I'd simply plug the old holes with solid steel threads and recut the holes to the correct location. Still you could also simply move to a new location about .188" forward, and drill and tap new mounting holes. The old holes with be covered with the bases, but I'd plug them anyway to help keep the junk out.