The case capacities of the 6.5x55 Swedish Mauser and the 6.5x54R Russian Olympic Rifle cartridge are almost identical.
I had one of those fantastic Match Grade Mosins back when International Firearms first released them for sale. I was lucky enough to be able to sort through several of them, before they were officially released for sale to the public.
IIRC, there were four different models offered, including one made for offhand shooting in the "running boar" competition.
Three of them had slightly modified M91/30 type receivers, with special stocks with length of pull and cheek riser adjustments. All were built for off hand type shooting, prone shooting, kneeling positions. There was one model, made at the Vostok facility that had a modified receiver. All had modified bolts. I really disliked the bolt modifications as the bolt knobs were quite small and hard to grasp.
Anyway, I started with the loads listed in the Hornady Reloading Manual for the 6.5x55 Swedish Mauser and worked up from there. My rifle had a 1-7.8 twist, with a long throat. It much preferred bullets such as the 140grn Sierra SPBT HP and heavier/longer.
I found max 6.5x55 loads seemed to be the sweet spot for the Sierra SPBT HP bullets I used.
The micrometer adjustable diopter rear sights were excellent, as was the hooded front sight with inserts.
Hope this helps.
