I cut the barrel to 19" on a Tikka T3 chambered in 308. It weights exactly 7 lbs with a Burris FF-II 3-9X40 on it. I'm thinking about going to a 1-4X20 on it for next year. Would be closer to 6.5 lbs.
I'd use the model 7 action. The action is a little shorter and lighter than the SA 700, but it actually has a larger loading/ejection port making it easier to load/unload.
IMO 308 is better than 358. The 308 will shoot handloaded 200 gr bullets that will do anything you can do with 225 gr 358 bullets plus you have the versatility to shoot 150-180 gr bullets that make it more versatile. A 358 bullet is less than the thickness of a dime larger in diameter than a 308 bullet. It doesn't make a hole enough bigger to matter and in similar bullet weights the 308 will penetrate deeper.
From a 20" barrel you still have enough MV from a 308 to use it out to 300-400 yards. It's not just a close range gun.
