Critical % Multiplier (Fallout New Vegas)

With the exception of the Explosives skill, including the assorted missile and grenade launchers in the game, all weapons have a Critical % Multiplier. This statistic is multiplied by the Critical Chance of the player to determine how likely any successful attack with a weapon will do bonus critical damage.

Affect on Critical Chance
Assuming a base line player with a Critical Chance of 5% (from 5 Luck and no other traits, perks or items affecting them) then the 10mm pistol (Fallout: New Vegas) (with a x1 Critical % Multiplier) will do critical damage 5 times out of 100.

The same player character firing a Sniper rifle (Fallout: New Vegas) with it's x5 Critical % Multiplier would critical 25 times out of a 100. If the player character has boosted their Critical Chance to 20% the Sniper Rifle's x5 critical % multiplier means every successful attack would cause critical damage.

Meanwhile, weapons like the Sawed-off shotgun (Fallout: New Vegas) and Light machine gun, that have a Critical % Multiplier of 0, can never have a critical attack.

Affect on Damage Output
(Note: The in game DPS statistic doesn't appear to take Critical Chance into account which can result in some weapons appearing less or more powerful than they really are.)

Each weapon has a set amount of Critical Damage that, for most weapons, is roughly the same as the base damage. The 10mm pistol (Fallout: New Vegas) for example, it does 22 base damage and an additional 22 damage on a successful critical attack. Exceptions to this rule include the Anti-materiel rifle which does 110 base damage but only 80 critical damage and the Abilene Kid LE BB Gun which does 4 base damage but 70 critical damage.

What this translates too is that a baseline player character with a critical chance of 5% will do, on average over 100 attacks, with a:
 * 10mm pistol (Fallout: New Vegas) ( x1 crit % mult)
 * 2200 base damage   110 critical damage    for 5% extra damage
 * Sniper rifle (Fallout: New Vegas) ( x5 crit % mult)
 * 6200 base damage
 * Anti-materiel rifle ( x 1 crit % mult and lower damage)