Is there any difference between the 6mm BR Remington and the 6mm BR Norma cartridges ?   Do the both use the same cartridge brass ?

Thank you for that.  I was searching last night and think that I discovered that the 6mm Dasher also uses the same brass but it fire forms pushing the shoulder forward.  The case length shows the dasher being .020" shorter .  I guess that happens because the body is being lengthened and the neck shortened in the fire forming process.
The reason I asked is that yesterday I acquired 200 rounds of primed Remington brand small primer 6mm BR brass.  I think I will start looking for a barrel for my TC Encore with preference for the Dasher.  The Dasher shows about 200 fps higher velocity with all bullet weights over either the Rem or Norma BR.

If you go with the Dasher, look at the barrel twist. I went through a similar project, and you might go with maximum accuracy potential, a 1-7.5 twist, and load good 105-115gr bullets. Might just start with Varget powder, and call it good. Best of luck with it.

I was in the first 10 shooters owning a Dasher when they came out shooting 1K Matches 20+ years ago. a great little round. But over the years its shown that A 105 gr bullet going out around 2950-75 is a sweet spot.the extra velocity just helped burn out the throat quicker. Also the short neck keeps you limited to what bullet being used. The 6BRA ( 6BR Ackley)  gets you to that 2975 velocity but with the longer neck you can use a variety of bullets with different  ogives  and not have to cut your leade or throat to match. A Sierra has a blunt ogive to a Berger with the longer ojive.Just something to think about.....

It's a fun topic. This Encore barrel would likely be a custom, and the chamber would likely have been cut with a modern reamer, with follow on throating, lead, etc. 

If it doesn't have the relatively quick barrel twist, and throated for long hybrid bullets, a 1-10 twist Dasher would end up being about a 243 Win. A long range sweet spot, might even be a bit under 2900 fps. 

It can be a rabbit hole, or maybe prairie dog hole. I don't compete, but it's a neat thing to watch bullet trace, through the scope, all the way to a seven or nine hundred prairie dog hit.