Weapons switching during fire

[Myst112 10]

whenever i fire with my rifle be it zoomed in or not, after a few shots my lower right menu appers, and after a few more shots it changes my weapon to the one that was in the menu, its quite unplayable :(

do for example if im firing with my m16 and the menu appears with binoculars selcted, after a few shots i auto switch to binoculars :/ :/

[kklownboy 43]

Sounds like a keybinding isssue, and or your Scroll options and action keys are the same asyour fire weapon key?