Re: .308 from a 16" bbl
The velocity drop from a 22 vs 18 vs 16 barrel is something I've research a lot as of late (buying a 18" DPMS LR308L). From most data I have seen, a 150 gr .308 load seems to have a large gain in velocity to about 15-17" of barrel. For every inch after wards you're gaining 25-50 fps.
A 16" bbl will spit a 150gr pill out at mid 2600fps up to mid 2700's, where as a 22" will be in the high 2700's to mid 2800's. (since the relationship of bbl vs velocity is not linear)
Overall you give up about 200 yards or so of range (16" vs 22"), but you will still be supersonic to 600 yards with a 16" and supersonic to 800+ yards with the 22". At 400 yards either load will have around 1400 foot-pounds of energy. A .223 pushes about 1200 foot-pounds at the muzzle, for comparison.
Numbers aside, you need to consider where you will be shooting. My terrain here is quite hilly, so a shot past 600 yards is very hard to achieve here, because these pesky hills and ridges tend to get in the way. Thus, for me, a shorter and faster handling 600-yard rifle offers a marked advantage over a larger and slower handling 800-yard rifle, especially since a 800 yard shot is very unlikely to occur due to terrain.
As for accuracy vs bbl, I am in the school of thought that bbl and accuracy have little to no relationship to each other. In the olden days longer bbl = longer sight radius = more accuracy. In the modern day of optics, a shorter bbl can be just as accurate as a longer bbl. Optics have an "infinite" sight radius, after all. Main thing is, is the bullet stabilized by the twist rate, and is the action and loading consistent enough to put it in the same place each time. I bet if you took that SOCOM that shoots 3 MOA with a 16" bbl, and extended to 22", it'd still shoot the same 3 MOA.
