>>"timing" the barrel so that the front sight aligns at "12:00" on the receiver is one big pain in the arse)
The problem there is that you really need a big box of different-thickness shims, to do it right, so that you can get the right timing.
On inch-pattern variants, yes, the shims are the ticket. All the ones I've fooled with are metric-pattern (Austrian) and shims are *possible* - if you have a good assortment of thin shim stock to cut from (paper thin stuff). Usually, max torque on the barrel brings it up short of the 12:00 mark, so the barrel shoulder's got to be evenly filed down.
I use a hunk of 2x4 with a hole bored nearly all the way through, with a piece of spent .308 brass secured in the center as a pilot. Two old-fashioned auto ignition files flank the hole. Just drop the breech end of the barrel down on the pilot, spin it between your palms for a minute or two, then remove and try the fit. Repeat as needed; only break out the shim stock if you over-cut the barrel shoulder.
Learned the above trick in the WECSOG (Wile E. Coyote School of Gunsmithing) ;-)