Apologies in advance, I know this has been discussed to death but I'm hoping I can get a definitive answer from players much more experienced than myself. The most effective Gatling Raid.. bullets to attack bonus.. has it been determined or is it pretty much an endless debate? I've been going with 10 bullets / 114 attack up until now but I'm just now getting into optional content and also trying to maximize damage on Mega Apples. (Currently Follow Me, Slumber Fog, >, Fragile, Great Booster, Gatling Raid)
If you want to maximize total damage output you need to use all your upgrades on Bullet Count. It's important to know that this is only relevant for Gatling Raid and not any other attack, and it also assumes you are going to buff up Rudy the best you can before using Gatling Raid. Using Lock-On is a must, because if you don't, some bullets have a chance of missing, which brings down damage enough to make other ARM upgrading strategies worth considering..
So, yea, bullet count is the way to go ... just make sure you setup Rudy appropriately before attacking to maximize total damage.
In that case put it to sleep else you won't have "time" to use Great Booster + Brave Seal+ Fragile + Offense Zone before Gatling raiding it to death.
Have Emma at Best luck status else sleep (or Paralyze) may fail to take effect though by level 88 Great Booster + Gatling Raid + Fragile and Rudy should do 100,000+ to it gaining over 1 million exp per Mega Apple killed.
Though Lock on Plus for its upgrade is best for Mega Apple killing the upgrade is worthless once you have level 100 PC's ie under Lock On Active as long as Rudy has 25+ FP he can use GR EVERY turn instead of every other turn.
Hence for the 3 Lock on Upgrades Active is easily the best one for super boss killing though Lock on Plus is better until you hit level 100 but once you chose 1 of the 3 upgrades its permanent.