Well, I define "long range" very different than some, and then there is ELR. Using the age old NRA standard for LR (800-1,000yds) or the standard some of us use ( 1/4 mile increments for SR, MR, LR, ELR) a properly loaded 50BMG in an appropriate rifle can shoot some fairly good groups at 1,000yds and well, well beyond.
Is the 50 BMG a typical "competitive" 1,000yd BR round? NO, but in years past, I've competed against a couple of bolt guns in 1,000yd BR, and as an old 50 BMG shooter myself, it does come into its own at ELR. However with the introduction of higher BC bullets in smaller calibers and more efficient cases, it has fallen out of favor with many.
We used to "play" with 50BMG rifles by shooting 55 gallon drums and car doors at 2,000yds. Try that in winds with your 6 Dasher.
( Full disclosure: I am a huge 6mm fan and own several various cartridges and rifles in that caliber.)