Well, I can say that on my High Power 40 cal, a break in period was needed. It took about 200 rounds or better to get it running 100%. I tried different loads, and finally run some cheap wolf steel cased ammo through it, and believe it or not, I think the steel cased ammo helped wear in the gun, because after only about a box of that stuff, all of a sudden the High Power would shoot everything.
I think the steel cases cleaned up a burr or something on either the extractor, or feed ramp, but I really think it was the extractor, because steel cased ammo has a reputation of being hard on extractors, so in this case, it helped clean it up, that or maybe the bolt face. At any rate, failure to feeds went away.
However, normally I don't think just shooting a gun, fixed an unrelilable gun, but sure helps identify an unreliable or reliable gun in most cases.