If no one turns the CV, you can easily sink one from 20k. I have done so a few times.
Seems most folks ignore any bombers that are flying up so high, so yeah.
I will admit that a LOT of the attacks I've seen recently on cv's (from both sides) seem to be around 7-8k, instead of the standard 10k. Increased accuracy comes at a cost though, as 7-8k is solid for a good 5" gunner. I haven't lost many level bombers to CV auto-puffy. The last time I lost a bomber was on a return trip from a strat raid in the G4M1. Set my #3 drone on fire within a minute of entering it's range. Other than that, the worst I generally get is a fuel leak, followed by a PW.
Dive bombers are a different animal.
SBD's get within puffy range, then explode. Ju-87's get to dive point, then explode. The only dive bomber that survives to drop (and even escape most of the time) is the D3A. Least that's how it feels to me. lol It's been so long that I've honestly forgotten if the D3A has an AP bomb now...
Wouldn't matter all that much since it wouldn't be very effective against anything but a DD, and even then I don't think it could sink one.