My 'smith says that rifle barrels are like people, all of them are different.

I test for sporting rifle accuracy with Eley, Lapua, RWS, and Wolf mid-grade ammo.

RWS Target Rifle has been my starting place for testing .22 rifles for a long time. I've only had a few rifles that wouldn't shoot good groups with it. One of them being a particularly accurate Marlin XT22VR that didn't shoot good groups with this variety of RWS, but will shoot Lapua Biathlon Xtreme better than any other brand and style that I've shot in it.