AR-15/M16 barrel diameter, front sight base

Factual Questions
1

I’m gathering parts to build an early-pattern AR-15. With the current hysteria, pars are a mite scarce. It used to be that one could buy surplus military barrel assemblies quite easily. Those seem to have dried up. New-production barrels all seem to be heavy barrels, or else contoured for more modern M4 variants. I did find reproduction ‘pencil’ barrels (currently out of stock), but they are not assemblies; i.e., there is no front sight base. In searching for front sight bases, I found that there are ones designed for ‘flat top’ (no carry handle) rifles, ones for heavy barrels, and ‘I have no idea whether this will fit’ ones.

What is the inside diameter of the barrel holes of the AR-15/M16/M16-A1 front sight base, as used on early-to-'80s production ‘pencil’/‘lightweight’/‘standard’/‘USGI’ barrels? Alternatively, what is the outside diameter of such a barrel where the front sight base goes?

2

All of mine are Colt, late to mid 90’s, so I can’t tell you.

As with all things however, there is a proper place for self-titled experts!

There’s some right dicks over there, and it’s easier to get banned than it is to sit in a chair, but there are some folks who know their stuff. That’s where I go for AR info.

3

Thanks for the lead. I didn’t see a search box (or a ‘register’ box, for that matter), but a google search on the site seems to indicate the number I’m looking for is 0.625 inches.