I've been building AK for the past 2 years, mostly form Tapco style flats. As most AK builders know, these receivers need some tweaking to make the build function properly. Is this similar to the "adjustments" needed to make an Enterprise or Century FAL receiver work? I'm looking for some reference point for the amount or work required before I buy my first kit and receiver. Also, what about barrel fit? Will I need to have lathe work done to get the barrel to index?
A FAL barrel can be timed without a lathe. If it over indexes you can shim it, if it under indexes you remove a little material from the barrel shoulder. Just be careful to remove the material evenly all around the shoulder, about .001 at a time and re-check the timing.
From the reports I hear, the latest generation Century receivers are much better than they used to be. But may still require some fitting.
I've lucked out with the FAL builds so far. I've used Imbel receivers and kits and so far the barrel has indexed correctly on them. The locking shoulder has been the Incorrect size but oversized by a few thousands and I was able to size them to the right thickness with a diamond knife hone cut to the with of the bolt contact area. The only trouble I've had is screwing in the barrel. I ended up making a barrel vise out of 2 4"x6" steel plates and some scrap pieces of oak. The 4"x6" is probably overkill but it wooks good and all it cost me was 6 bolts. I saw somewhere a way to time the barrel if some of the shulder needs to be removed. The guy took flexible grinding disks at least 4 " diameter and cut the center hole large enough for the barrel threads to go through but not the shoulder. He then screwed it into the scrap receiver stub loosely with the abrasive side towards the barrel shoulder and turned the grinding disk many many times until when installed on his good receiver it times correctly.