There have always been lot to lot differences, even in top ammo. Competitive shooters have lot tested for decades. Even in the less expensive ammo, you see differences in lots. Right now, ALL makers of 22 RF are cranking out ammo as fast as they possibly can. What used to be top notch ammo, like Eley, has lots of reports of poor groups, flyers and inconsistent loads. If you scan the Rimfire Central forum, you see the same complaints about Winchester, Remington, Eley etc. I believe that as supplies stabilise we will see a return to better QC and more consistent ammo. I posted some ammo test targets on the 1710 Anschutz thread. You can clearly see differences in the groups by brand and quality of the ammo.
http://www.outdoorsmenforum.ca/showt...=429433&page=2
For now, I would buy a couple of 50 round boxes and test shoot it, before stocking up on a large order of any ammo. The trick is getting the retailer to hold a case of ammo of the same lot for you while you test shoot the first 2 boxes. Places like Nordic, and Precision are more likely to do that for you than CT.