I've run 6.5CM with both can & brake. I prefer running a can personally (TBAC Ultra 7)

In case you don't, make sure to run your magnification out. Don't zoom into the target at 25x, 15x works out to 1000, lower magnification makes it much easier to spot your own hits/misses. Helps to have a dusty background as well.

As a friend to spot for you as well initially until you find your sweet spot for magnification.

If you're not interested in getting a silencer, I'd definitely get a brake. Don't go cheap. Get one of the best brakes you can. Anything in the top 5, but skip any of the mediocre or lower end ones.

I've never known groups to open up with a brake or can. My groups are always smaller with a good brake over a bare muzzle.