I've been into Turn 5 with 481 accuracy and haven't noticed any misses, so either it's just the same RNG luck as you or the cap is indeed lower than 483.
Is it worth waiting the 20 or so seconds for B4B to come back up after IR to always pop them at the same time? I'm just wondering if there's enough multiplication between the two of them to make up for not just popping them as soon as they are available after the first usage. I would test this myself with parsing but I'm a console plebeian. :c