How does weapon experience work in Torn?

TornLife researched this question and found the points below; each one is taken from the sources cited. TornLife could not write them up as a full answer.

Where is it shown and how does it apply per weapon type or per individual weapon?

• Simplified mechanics per the wiki: attacking someone with roughly 75% of your total battle stats or higher gives FF 3x. The lower the target's stats relative to yours, the closer FF tends toward 1x.^[1]
• Hitting anyone with a battle stat score higher than the player with the 1000th-highest battle stats gives a full FF of 3x. This follows the 16/01/18 patch that added a default maximum fair fight bonus for attacks between very high-stat players and reduced the requirements for maximum FF.^[1][2]
• The wiki says the fair fight (FF) multiplier ranges between 1x and 3x and applies when attacking a target with battle stats similar to your own.^[1]
• Suppression debuff: Defense and Dexterity are reduced to 1/2^D. Level 1 removes 50%, level 2 75%, level 3 87.5%, level 5 96.88%, level 10 99.90%. For example, 10,000,000 becomes 5,000,000 at level 1 and 9,766 at level 10.^[3]

• Distraction is the group-attack mechanic in Torn combat. It governs what happens to a defender attacked by multiple players, applying debuffs under a 'Distracted' status effect that weaken the defender's effective battle stats. It is not a Crimes 2.0 mechanic.^[4]
• FF depends solely on the battle stats of attacker and defender. JTS (Journal of Torn Science) derived the formulas, which use each player's battle stat score to form the FF ratio. The captured text does not include the formula itself.^[1]

Has it changed over time, and what do players say about it?

• The Distracted effect is applied to the defender but the level is personalised to each attacker. If one player has made an aggressive action within the last 30 seconds, every other attacker sees level one. Two players give level two to everyone else, and so on.^[4][5]

How is weapon experience gained and how much per hit or attack?

• Aggression debuff: the defender's chance to take a turn against each attacker's turn is 1/(D+1), where D is the Distraction level and D+1 equals N, the number of players who acted aggressively in the last 30 seconds. With two attackers the chance is 50%.^[6]