I agree with PixMan, Ugima is the only thing we put in our Citizens. Almost every part we make has +/-.0001 tolerance on the diameters. One part we make is .0469 +.0001-.0000 at each end and .063+/-.0001 in the middle. We can hold that on our L-20 using Ugima material.
You have to use very good guide bushings and adjust them properly as well. Don't buy used or no-name guide bushings, Get the absolute best you can. The upfront price is insignificant when you amortize it over thousands of parts.
Tinmuk
*********************
Any problem can be solved by the proper application of heat!