Help! Weird keyboard lag

[Captain Flapjack]

Having an issue with keyboard lag. Walking around works perfectly fine UNTIL i start shooting a gun with the mouse, then it takes multiple seconds sometimes for the game to register a change in key press on the keyboard. I've tried everything I can think of including turning down the polling rate of my mouse. Both peripherals are plugged directly into my motherboard no USB hub or anything? Any help appreciated. This is ONLY happening in this game. I've been playing other FPS games with zero issues.

[Diogenes49]

some gun manufacturers use a capacitor that takes time to charge you have to hold the fire button to get it to fire