I believe that CZ recommended 5nm or about 44 inch pounds for the action screws. Personally, I would consider this on the high side of things. The screw torque setting can be adjusted by the trial-and-error method of starting low and gradually tightening the screws, stopping when groups settle down. A second thought would be to look at the barrel in its stock channel. CZ is somewhat notorious for not centering the barrel in the channel. Sometimes CZ uses a small amount of glue to bed the recoil lug and other times they leave it unglued. If the barrel happens to be up against one side of the stock channel which can lead to accuracy problems, you might try centering it. This can require chipping out the glue if it's there though. I would double check the scope mounts to be sure there still properly tightened and then play some with the two action screws. Your definitely on the correct path by experimenting with different ammos. You didn't mention your CZ 527's 223 rifling twist, CZ offered both the 1-12 inch twist barrels (earlier in production) and later began to swap out to a 1-9 inch twist barrel. If your barrel happens to be a 1-9 twist a 50-55 grain bullet with its higher velocity and consequently higher RPM's the bullet may take a bit longer (more than 100 meters) to settle down. The common analogy being a child's spinning top, at first it wobbles and wanders around until it finally settles down and goes to "sleep", then remaining stable and mostly in a single spot. One of my CZ 527's in 223 with a 1-9 twist barrel shoots quite a bit better groups at 200 (substantially smaller than twice the 100-yard target) yards compared to a normal 100 yard groups. I would think the rifle capable of better accuracy than 2 inches with the S&B 55 grain FMJ ammo but then again, it's also possible your rifle just doesn't care for this load.
