Framerate goes down alot when changing weapons

Yeah i encountered this problem after i got a new computer. My FPS is normally 100-300 but when i change my weapon through the top screen weapon UI, you know what i’m meaning, it goes down to 30. It’s not a big problem, but it’s annoying and distracting though. Anyway, i realized that amount of the weapons in one slot affects how much it lowers your FPS. Any solutions? Specs if needed.
OS: Windows 7 Home Premium 64-bit
RAM: 4GB
GPU: Ati Radeon HD 5770 in Crossfire
CPU: Intel Core i5 750

Try quick weapon selection in the advanced part of the keyboard menu. But 30fps is not exactly a problem, I used to have to play at that speed all of the time.