Lost accuracy with new mouse.

Hi, I bought a new mouse (Razer Mamba) 2 days ago, I had tried my friends Mamba before, and I just loved the way it was shaped! But when I bought mine I couldn't oneshot at all, and I considered myself a decent AK-user before, but now I can't control the recoil, even when I try I fail miserably. I think the reason I lost my accuracy is because my other mouse (X7 718-BK) was made for Claw grip, and the Mamba is Fingertip/Palm (one of the reasons I changed mouse was because my hand started aching after 3-4 hours). But when I used my friends Mamba I was better than with the x7 mouse, because of the better ergonomics, but now I can't aim at all
Do you have any practises that I can do to increase my acuracy?