I'd be most dubious about these supersonic to wherever figures. Even on Sierra Infinity V.6 that uses inaccurate G1 drag-curve BCs, the 155gn Lapua Scenar at the 3,000 fps MV you could expect from this loading in a 30" tight-bore barrel target rifle is only barely supersonic at 1,300, and it takes over 2,800 fps MV to repeat the trick at 1,200, although that might just be possible in a 20" barrel rifle at way above safe pressures.
Or then again, these sniper types like shooting 10,000 ft ASL in 100-degree heat in deserts, so who knows?
However, run the best of the the 0.308" 155s at 3,000 fps using Bryan Litz's experimentally obtained G7 BC value through an appropriate ballistics program and you get rather different results - 1,151, 1,059, and 1,010 retained velocities at 1,100, 1,200 and 1,300 yards under standard ballistics environmental conditions. (59F etc).
Your triple role 6BR 17lb rifle sounds eminently sensible. I can say that hand on heart as Walker Rifles has just built same for me but in 6XC, albeit only for the F-Class and BR LG roles in single-shot form. What you will likely find is that it takes a fair degree of paring to make the 17lb Light Gun weight limit with a modified F-Class stock. My gunsmith had to ask the UK McMillan importer to specify as low a weight as the company could sensibly produce for what started as a McMillan F-Class type. The cheekpiece has been moulded into the buttstock too removing the height adjustment bits. Even at that, I'm restricted to a 1" dia fixed power scope to keep weight down. (This is with the relatively heavy Barnard action that weighs around 3lb.)
Alternatively, there is the McRees MOD-MPSS aluminium allloy modular stock system where you can add, remove and swap bits for the different roles. I've done this with my Savage 12 action F-TR rifle using a 3" wide BR forend off the bench and a 2.5" wide varmint forend and bipod for F-TR. There is a tactical forend too. McRees Precision won't export them to Europe now unfortunately, but there is a Spanish version and that is being put into production in the UK shortly too getting around that problem, but we have to see if it will be available for the large number of actions that the US maker caters for. Also, it's a rather heavy bit of kit. (If you're interested in this stock system, see the August and September issues of the free UK based online TargetShooter magazine -
http://www.targetshooter.co.uk/
which has a two-issue write-up of my .223 F-TR rifle using it. September goes live on Thursday.)
For F-Open, the limit rises to 22lb, so you can take the lightweight scope off the rifle in its BR guise and mount a heavier and larger objective lens variable model not worrying about the extra pound or pound a half. So, you want a QD scope mount system - M1913 Picatinny or similar rail and lever mounts or similar.
You'll need a rail inletted into the forend as well for the tactical role to mount a bipod unless you have a mounting spigot for a Versa-Pod type moulded into the front surface of the forend (but I think that in keeping weight down, the forend may end up overly shallow for this solution). A rail adds a little weight and detracts from the rifle's performance on the front-rest.
The only other issue I can think of is getting the 6BR to feed reliably for the tactical role. 6XC or 6.5X47L, or its necked-down 6X47L wildcat will be simpler. It's not impossible to get the 6BR to feed from a 'standard design' detachable box mag. Here in the UK, Dave Wylde in South Yorkshire Shooting Supplies has built several such rifles now. I don't know which magazine is employed, but most likely the Accuracy International model, and knowing Dave's work probably on Surgeon actions.
Laurie,
York, England
