What are you wanting to do with the rifle? “Horses for courses,” or “tools for tasks,” the 6BR I would use for my sport is different than
@South Prairie Jim would use for his.
Personally, I like the added case capacity of a 6 Dasher over the BR - I can either run extra speed, OR run the same speed at a lower pressure (and I do the latter most often). But either or both of these rifles could just as easily be chambered in straight 6BR.
My two Dashers are built for PRS competition, meant to launch Berger 105 Hybrids:
• Both with Defiance Machine actions, one a Deviant and the other a Ruckus
• Both with Manners sticks with Mini chassis’, one a T4A and the other a Compact Gen2
• Both with TriggerTech Diamond triggers, one a flat shoe at 6oz and the other a curved shoe at 14oz
• Both with Area419 Arcalock rails, one a Universal and the other a tunable weighted rail
• Both have 26” barrels with 7.5” twists, one a Proof Research Competition Contour and the other a Bartlein M24
• Both have American Precision Arms Little Bastard muzzle brakes, one a Gen 3 and the other a Gen 2
• One has Vortex/Seekins rings on a Kahles K525i 5-25x56mm with SKMR3 reticle and the other has a Nightforce NX8 2.5-20x50mm with Mil-XT reticle
• Both have lead added to the forend to move the balance point (without bipod) to ~4-5” ahead of the front action screw, one rifle is built to be lighter than the other at 17.6lbs and the other at 21.2lbs
• I maintain segregation of brass between the two by using Alpha Dasher brass in the Ruckus and hydro formed Lapua 6BR brass in the Deviant
• Varget is king for Dasher case (if you’re building a straight 6BR, you could also try H4895 and be pleased)