I have a Springfield Armory 1911 .45, the Loaded Model. (PX9151LP) Every load that I've tried hits slightly left of where I'm aiming, so I'd like to move the rear sight slightly to the right. It has a fixed low profile combat rear sight that I thought I could slightly drift right. The problem is that there is a set screw in the middle of the rear sight that I cannot find anything to fit to loosen. It is tiny, and very hard to see, but it looks like either an allen screw or a torx - I simply cannot tell what it is, and I've tried everything. The manual does not tell what it is. I called Springfield, and the nice customer service lady told me a size that was obviously much too large. I do not have a gunsmith near where I live, plus this should be a simple matter. Ideas?

It should be a VERY small allen screw.

The smallest wrench in my standard set is .050". Might be a 1/16 " which is .0625". If it is metric, try 1mm or 1.5mm.

Even if you find the correct size Allen wrench, there is a good chance it will strip the head before the screw moves (experience speaking). I have bought the small Torx drivers, T5 - T9, from Brownells. There will be one of these that will be a tight fit in your small set screw head, maybe even a tap in fit. The Torx do not strip nearly as easily as Allens.