I'm thinking about getting a few bore lasers for my long-arms. I've my eye on the sightmark chamber bore line and am interested in getting one in 12 Ga. for my Saiga, one in 7.62x39 for my AK and have been looking at a comparable alternative caliber for my Nagant chambers, as they don't make 'em in 7.62x54R. The relevent specs for 7.62x54R are its shoulder diameter of 11.61 mm, its base diameter of 12.37 mm and its rim diameter of 14.40 mm... Subsequently I was looking at either the .300 Win (shoulder diameter: 12.4 mm, base diameter: 13.0 mm, rim diameter: 13.5 mm), .308 (shoulder diameter: 11.53 mm, base diameter: 11.96 mm, rim diameter: 12.01 mm) or .25-06 (shoulder diameter: 11.2 mm, base diameter: 11.9 mm, rim diameter: 12.0 mm) lasers as a substitute. Any thoughts? suggestions of a better alternative to the chamber lasers for my Nagants?