I am an avowed Colt fan, but I wouldn't get a 6920 for long range target shooting. There are many better options out there for the money.
The 6920 is a great defensive/duty rifle, but not the best use of money if you are wanting to shoot targets at long range.
The Colt CR6724 and Colt CR6720 Target rifles are much better for that if you are wanting to stick with Colt.
If you are willing to go something other than Colt, there are some really nice Target rifles out there. There are even some "mixed use" high quality rifles from BCM that can do both.
Personally, I would go with something like a S&W M&P or a DPMS with a 1/8 twist barrel if you want to shoot targets at long range and put the extra money towards a good magnified optic.