Gun and ammo stats
http://ducksoficarus.servegame.com
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If your engi needs charged for a merc they can also use it on their light flak, in fact charged Lflak does more dps than burst (+6.1 vs 3.6%) and is the highest dps ammo for light flak, although burst is recommended due to higher DPC and the nature of Lflak high ROF vs hull break time (charged is the next best mid-range ammo). That's not saying charged can't be reworked, but it's certainly not unbalanced - unlike incendiary and arguably greased (not mentioning loch)
Looking through that site, results are actually mixed with Light Flak. Against certain ships, greased is best. Against others, charged is best. Burst is always slower than Charged.
Kill times in order of Charged, Greased, Burst, assuming no misses. Number of shots in parentheses.
Normal clip size: 6
Clip sizes: 5, 7, 7
Squid: 6.42(7); 6(11); 6.96(9)
Gold: 6.9(8); 6.44(13); 7.38(10)
Junk: 1.44(4); 1.1(6) 1.68(5)
Gall: 7.86(10); 10.9(16); 8.64(13)
Pyra: 1.92(5); 5.34(8); 2.52(7)
Spire: 6.42(7), 6(11), 6.96(9)
Mob: 1.92(5); 5.34(8); 2.52(7)
So against Pyramidions, Mobulas, and Galleons, Charged is the best ammo. Greased is behind on both due to needing an
extra reload.
Against Squids, Goldfish, Junker, and Spire, Greased is best. Greased is ahead on these because it does
not need an extra reload.
Charged wins out over greased when it does due to superior
Damage Per Clip. Greased wins at other times due to superior
Damage Per Second when firing.
Looking at the numbers, this seems to be a case where the reduced clip size doesn't affect the Light Flak. Charged L Flak has only 5 shots, but can kill 3 of the ships in exactly 5 shots, so losing its 6th doesn't hurt it. All other ships would require a reload regardless if it hat 5 or 6.
In other words, it seems Light Flak is at one of those magic ammo counts where Charged is really good because it doesn't lose 20% or more of its clip (Only loses 16.6%), due to ammunition changes using proper rounding as opposed to integer rounding (always round down). If it did round down (the case on most guns), Charged would have 4 rounds and be worst of the three on the three it is best on.
I feel like this only supports the idea that Charged needs a lower clip size penalty to be relevant in other weapons. The only other weapons that get a reduced penalty and have more than 2 shots are the Lumberjack (6 to 5), and the Mortar (12 to 10).
If you're wondering, the Mortar can one-clip every ship in the game with Greased, even if it only just barely one-clips a Galleon. So Greased always wins in kill time for Mortars.