Occasional lurker and rare poster - but this caught my eye as I think you're setting out on a fun project with the makings of great results.
Maybe 25 years ago I built a 6.5X55 on an M38 base - NOS stepped barrel cut to 20", walnut stock, cock on opening, action bedded/barrel floated from approx 1.5 forward of the action, jeweled bolt, hi-gloss blue, Timney or Bold - I forget which. Worked up two loads - 140 gr Sierra and 120 gr NBT. Very accurate with both. Hadn't shot it in a few years so just this past weekend took it out to check zero and figure I'll use it this deer season. These were shot at 100 yards off a bench, .35 Rem target is the target on the left, 6.5X55 is the center target, NBT 120s. Both 3 shots, then an adjustment for a total of 4 shots each group. Scope on the 6.5X55 is an old Burris 3X9 compact.
IMO, the 6.5 bore relative to barrel thickness of the stepped barrel plus cut to 20" makes a very stiff barrel and aids accuracy... at least that was my theory way back when. Whatever the reasons for it, this rifle has always been a great shooter. Cloverleafs are the norm and one-hole groups when I do my part. Good luck with your project!
