I get the best accuracy with regular CCI 209's. I tried the magnums but couldn't seem to get the right load with those. The regulars seem to work much better no matter what loads I use.
CCI standard 209's. Have some Remington STS I picked up during the primer shortage but haven't worked up any loads with those, and probably won't given the current price of BH209.
When Blackhorn first came out I tried it out with the standard Winchester 209 primers out of a T/C Omega that I had. Worked great, no issues BUT the temp was in the 50's. Forward to Deer season here in Western New York and the temp was in the teens with wind chills below 0. That's when the standard 209 primer (FOR ME) was an issue. a couple of times they would not ignite the Blackhorn. I then switched over to Fed. 209A Mag Primers and there was never an issue again in any temp. Sold that gun to a buddy 15 years ago and to this day he shoots the same load and Fed. 209A primers and zero issues.