I would be willing to bet that it's a barrel lottery... some are going to shoot good and some are going to shoot great, you could easily have a 'match chambered' rifle that gets out-shot by one with a 'standard chamber'. Buy 10x of them, shoot them all and keep the one that shoots the best... but don't be surprised when 'next month' the 'stars of rimfire' don't align and it doesn't shoot as good.