Gunsmith

Sometimes, after successfully downing an enemy plane in Combat, a Weapon Modification will be awarded (in addition to Combat Points and bounty).

Weapon Damage Calculation
Do not trust the quoted rate-of-fire in the gunsmith tab. The displayed number is merely the true value after being rounded down. The true RoF is treated as (milli)seconds per shot rather than the displayed and rounded shots per second, and are listed below. Working out the true shots per second would be 1000/(weapon speed in milliseconds*(1-RoF bonus)), and then that multiplied by damage per shot to get the damage per second.

NB: The Autocannon and Flak Cannon shoot multiple submunitions with every shot. To determine their damage per submunition, divide the weapon damage by 20 for the flak, 2 for small autocannons, 3 for medium autocannons, and 4 for large autocannons.

Weapon Mod Types
Armor Piercing Rounds A straight damage-per-bullet increase at the cost of a critical hit reduction, Armor Piercing Rounds have a simple effect. They typically add about 20-25% damage and reduce critical chance by about 5; meaning since most guns have a base critical rate of 5%, AP rounds will usually nullify their ability to go critical. The damage increase is good, but if your weapon depends on critical hits to damage planes with high Armor Class or low Silhouette, this mod will severely reduce your ability to fight those planes. If your base gun damage is too low to break a given plane's armor class, the 25% damage boost is rarely enough to breach the armor class.

Explosive Rounds Explosive Rounds raise your critical rate by about 5, typically in exchange for a small damage percentage cut. The critical chance is enough to double the critical hits for most guns (though it is only a minor boost for Flaks), and typically more than makes up for the damage cut. Explosive rounds are especially helpful for breaking Armor Class, as criticals ignore Armor Class, or for hitting planes one would often otherwise miss. Howitzers make good use of ERs due to a 50% critical damage boost.

Extended Barrel The only mod with two guaranteed, and significant, positive effects, Extended Barrels or EBs find their way onto most guns in Skytopia. Typically adding about 20% arc length and about 10 accuracy, any gun type can easily reap the benefit of an EB.

Grease Mixing its negative and positive into one stat, Grease raises your rate of fire and thus your rate of ammo use. A rather simple damage % increase, typically around 10%, Grease is effective on any gun, though it does not increase damage from any single shot; slow rate of fire weapons have to fire at least twice in a row in order to benefit from Grease.

Improved Swivel Mount A simple arc width increase of about 20% coming with low to no accuracy reductions, Improved Swivel Mounts slightly increase your arc coverage. Their effect is most noticeable with flak cannons, though the boost is largely aesthetic.

Recoil Suppressor Extremely useful for the inaccurate Howitzer, Recoil suppressors typically add about 15 accuracy, and have a slight damage percent decrease (though Recoil Suppressors with no damage negative are common). Accuracy is less of a concern for other gun types, though Machine Guns and Autocannons will do a bit more damage to planes with small Silhouette.