Weapon Mechanics =

R Upgrade

The R (Rapid) upgrade makes any gun (including the peashooter) fire faster. If you pick up another weapon the R upgrade is lost. If you have a weapon like the spread gun and collect the R upgrade, the R upgrade is lost if you pick up another spread gun.

Machine Gun

The machine gun has automatic fire if you hold the B button, however if you mash the B button the gun fires even faster. The machine gun has a shot limit of 8 shots on the screen at once versus 4 shots on the screen at once over the peashooter so it is much more powerful than the peashooter.

Spread

Generally the most powerful weapon in the game. The gun fires a wave of five shots and you can have up to 10 spread shots on the screen at once. You can keep firing spread shots as long as there are less than 10 shots on the screen. This can be used to manipulate the wave of spread shots into a straight stream, although this technique is not as useful as it was in the first Contra game.
The health of certain enemies and bosses increases if you have the spread gun. This means that spread gun is not always the ideal weapon when running the any % category of this game. If you are doing a co-op speedrun and both players have spread, the health of certain enemies and bosses increases even more. You can refer to the weapons damage and enemy health spreadsheet for more details.

Flame

The flame gun has a standard shot that will disperse in 4 directions when it hits a target. If you press and hold the B button for 33 frames (just over half a second) you get a charge shot. The charge shot penetrates minor enemies like soldiers and when it hits a wall or an enemy that takes several shots to kill it will collide and expand into 8 directions. This is the only gun that can do more than 1 damage per frame.

Laser

A laser beam is fired and the entire beam will do 4 damage. Only one beam can be fired at a time with this gun. If you fire one beam and then fire another beam the first beam of laser will disappear. This weapon is not used in speedrunning.