Re: 6.5x47 vs 6.5x55
I shoot both and I believe the 47 has better inherent accuracy, I shot a match this weekend at 1,000 yards and the top two shooters were using 6.5 x 47 L (130 Berger VLDs), I came in second. We competed against the normal array of of SAUMs and WSMs and the wind was no issue Saturday but was on Sunday and 6.5L held reign both days.
If you must shoot 140's the 55 may prove to be the better round and then you might as well go up to 6.5 x 55 AI which is a ballistic twin to the 6.5 x 284. I think the case capacity of the 6.5L is too small for 139 and 140 grain bullets.
Barrel life on the 6.5L is good I just dropped my action and a blank to be re-barreled it had about 2,300 rounds and was set back at 1,700 rounds. The old barrel would no longer hold in the vertical and I was scoring some 8's and more 9's than I should have at 1,000 yards. I know there are people out there that claim 3,000 or better rounds out of the 6.5L, my experience is not that good. When I shoot F-class the barrels sometimes get smoking hot after 22 rounds if the conditions are right the 22 can be fired in an easy 5 minutes.
I think the 6.5L will get more use in F-class as time goes by, compared to the 6 mm BR we are just learning about the 6.5L. Benchrest shooters claim the 6mm BR is more accurate out to 600 yards and I do not dispute that for a very fast 5 shot group. In F-class we fire a shot the target gets scored comes back up for another shot etc. so we are taking shot over a wider range of time so the wind has a better chance of changing and the 6,5L has less drift the 6mm BR and this may make it the winner when the wind picks up. I also shoot the 6mm BR as a practice gun for better barrel life.
A long-winded reply and I focuses a lot on F-class as that is where my experience is with the calibers you mentioned, except for deer hunting for a long time with the old Swede.
Hope this helps,
wade