Don is right on as usual
you want to measure the barrel and colt springfield and para are around .5785. (usually) We bought the World Class bushing line and fixtures from George Huning. The angle bore bushing he designed allows the barrel to lock up fit well and not spring.
the slide hole is a different story. .701 is the std bushing. I have seen para's that went to .715! Clark makes the 3 finger bushing when you go over the .706 Id size.
we make a .701-.702 as the std. and a .705-6 for the bigger slides. I suspect some others make big ones also
as a result of reading on the fourm here we are going to come out with a .700 bushing for the drop in at home guys. (the smallest ID. I have seen is .699 but only 2 times)
A side note here.
Brownells has a pretty high bar. If they do not profit 750.00 per colum inch per year the part is dropped from the catalog. If you have a favorite part that is dropped call the manufacture. they probably still make or have it. Just because it got dropped in the catalog does not mean it is not available from the manufacture.