I'm not very 'expert' but I do have a Mark II. I think 200 rounds is not nearly enough to break that gun in. Also, I think you just haven't found the right ammo for it yet. I use Federal bulk .22lr in a red box and I have had very good luck with it. My Mark II eats anything I have put through it. But I did buy it used and I do believe it has many rounds put through it. Some people have good luck with .22 CCI ammo. But for me, the Federal bulk in the red box works beautifully.
What brands have you been using?