yeah, there are like 5 threads on this somewhere, but when I enter "break in ammo" in the search I didn't get anything either. then I tried searching from the forum home page and got a bunch of threads.
High impulse ammo. something hot.
the logic behind that it to cycle the action firmly and allow it to wear faster i guess.
frankly, tho I dont think it makes a lot of difference, if you are aware that you may experience some failures till it does in fact break in. Mil surp was what I used myself, on the first gun then the second got broken in by Terra for me, and by the time I got it, it ran just fine with barnaul and wolf as well.
my advice is to run it until it runs right. dont stop with "200" rounds. get some rounds thru it and have fun. put 400 thru it, then check all screws and bolts for tightness and lock tight any that seem questionable or loose (except the barrel bolt)