can anyone recomend cz 452 varmint 16 inch barrel do they like .17 v max poly tip 17 grain,is there any downside to a shorter barrel.

As far as which ammo a gun prefers, this differs from gun to gun even of the same make and model. Some can be consistant, but best to try a little of everything to see which your gun likes best. Everyone has a favorite in thier gun, but they got there doing the same thing... trying different ammo to see which is best for them.

Rimfires can be strange creatures. Two of the same rifles shot side by side can prefer different ammo. You just got to try a bunch and find out which your gun likes.