I have a pair of rifles in9X57. For light plinking loads I use 9mm .355 dia. bullets, both cast and jacketed, that were designed for use in the 9mm Luger. I have also used 35 cal. .357 dia. pistol bullets as well with no issues to speak of for light loads.
I also use standard .358 dia. rifle bullets but I run these through a Lee push through die to reduce them slightly to the standard 9mm bullet dia. of .355" just to be on the safe side as both my rifles have tight chambers and I don't want any chambering issues with these bullets.
For loading data I use the 358 Win. STARTING loads as found in several loading manuals and work up from there. I have also used Trailboss with good results in several bullet weights.
The two 9X57 rifles I have are among my favourites to take to the range, both are nicely balanced and handle quite well.