Kickback pic
kickback_pic determines which animation frame the player's current weapon is in. Generally, scripts can just use the constantly updated gamevar weaponcount instead because the executable basically performs a "getplayer[THISACTOR].kickback_pic weaponcount
" every tic.
If kickback_pic is set to 1, then it will continue to increment and cause the currently selected weapon to fire, returning to 0 when the weapon reaches its total firing time.