I want to ask everyones opinion on what should do, I am stuck between a 6 dasher or a 6xc. Is there a real diffrence in performance? The rifle will be a shoot 600 fclass ,and some coyotes, maybe even a deer or two. Are both just plain accurate?

For making the dasher brass I will use the same norma brass my mrs uses in her 6br. And a will get a hydroform die so I don't kill the barrel fire forming all the brass. The xc is avaliable also.

6mm xc
You dont need to hydroform it and have factory ammo if you want it.

I'd go with the Dasher if you are going to stay with the 105 class bullets and not going out past 600 yds. If you are going to go out to 1000yds, I would utilize the extra HP the 6XC provides, plus the 115 class bullets.

Forming cases for either is about the same amount of work.

I can buy the 6xc brass but I will have to dasher brass. that is what im told

I wonder if it would be a good idea to just skip both and go a 6.5-284

The 6xc and Dasher will give significantly (`2x longer) barrel life than the 6.5-284 and be less expensive to feed because bullets are less expensive and less powder used. Typical barrel life is 6.5-284/1200-1500rds, 6xc/2500-3000rds, Dasher 3000+rds

The 6.5-284 will have a slight wind drift advantage at 600 with 140gr bullets, more significant at longer range. Run some numbers through JBM Ballistics webpage. 6.5-284 and 6xc will recoil a bit more which can add up over 50 shots.

Inherent accuracy edge probably goes to the Dasher, but all three can be made to shoot bug holes.

Dasher brass can be fire-formed during a match with good results. Lapua brass availability has been good. 6xc brass can be formed during match from 22-250, and off the shelf brass is out there but availability and quality has wavered over the years. 6.5-284 brass is available off the shelf, good quality, but more expensive.

My recommendation for 600yds stands with the Dasher.
Pick your poison. All three will work for your stated purpose.