You only need glancing snapshots with the 30mm... You can't do that with the 20mm. The 30mm allows you to keep your lines really smooth and E-efficient. You only need to intersect the target for long enough to shoot a couple of rounds. What you lose in flexibility of gunnery, you gain in ACM flexibility. I can easily say that flying the 152 has made my gunnery suffer.. What I've gotten used to is to let the ACM do all the work, and then just fire 2 rounds of 30 on an easy target (close and/or relatively still) for a kill.
Interesting. Yes, that is generally the type of shot I take with the 30mm - target is slow and I've got a 50-100 mph E advantage swooping down (or up - the climbing target is pretty easy too).
However, with this style, I feel like you get stuck either
1) Cherry picking
2) Waiting for your opponent to make a mistake like trying to climb Co-E with you
3) Flying a long ACM engagement waiting for your target to blow his E while you similarly get into a situation that's hard to fly away from. I've gotten into engagements where I get on my opponent's tail for 30+ seconds while he violently maneuvers and I follow him, but can't get the kill because taters aren't landing.
(Note: while I feel picking is certainly legitimate, I'd like to have a reasonable chance at ending a direct-confrontation quickly WITHOUT relying on my opponent doing something dumb)
Any advice given my concerns?
Separate question: would you advise taking medium or medium-high speed (speed referring to target speed) snapshots with the 30mm?
All in all, it's an interesting compromise - less flexibility in gunnery for better ACM. Seems great for 1v1, not so good for complex multi-plane engagements.