If you’re looking for a more direct answer. It would be .22lr in Cz 457. Those bmr are sweet though haha never shot one just looked at em a couple times.
Can you give more details? Gonna shoot a lot? How far? A lot meaning hundred of rounds a month.
I can shoot in my backyard, so 100+ rounds/month easily. As far as distance, 100-150 yards for paper; max 50 or maybe 60 for squirrels.