I picked one of these up last Friday and have put about 200 rounds of CCI SV through it alongside 400 rounds of Aguila SuperExtra Subsonic HP's. At 50 yards average groups were between 0.5" and 0.6" with the CCI SV and between 0.6" and 0.7" with the cheap Aguila stuff (just picked up a brick of it to have fun plinking really). Haven't gotten around to testing out a bunch of different flavors yet, but I imagine the performance will be similar since what I've seen
Something to note is that the action really does seem to break in. When you first pick it up and cycle the bolt, it feels surprisingly stiff to open and close. After the first hundred rounds or so you could feel it start to lighten up, and it's much smoother now that I've put more than 500 downrange. The forwards/backwards bolt travel was always pretty slick, it's just the opening and closing that have eased up.
Probably the most interesting find was that attaching a Thunderbeast .22 Takedown led to a HUGE point of impact shift. In the past the .22 Takedown has shifted POI by maybe 1-4 tenths for me depending on the gun, but this Bergara shoots 1.3 mils higher with the can attached than with a bare muzzle. I didn't chronograph any ammo to see if there's some kind of velocity change going on, but I was very surprised by that. I love shooting subsonic suppressed .22lr though, especially from a bolt gun, because it's just an unbeatable level of quiet.
One last thing I'll likely try, after testing out the various ammo brands, is re-torquing the action screws as well as swapping it around into my MPA chassis to see if those affect the accuracy in any measurable way. I know some rimfires seem to respond quite well to that so I may as well check it out and see if there's a torque level the action prefers or if dropping it into a known quantity (the MPA) makes any difference either.