Question for you who size your pellets..

Doing it to improve general pellet consistency is perhaps useful, but please do not get too fixated on the idea there exists a magic number. Pellet barrels do not have a preference for a singular head size down to the hundredth of a mm. Within a range of 0.03 – 0.05mm, one tin of pellets will often have as a good a chance of grouping well as another. They just need to be big enough to be supported by the rifling (ride the rails, so to speak) but not so big they extrude into the grooves and smear against the walls.

So when you conduct this sizing experiment and find a size that your AG seems to prefer, it is true really only for that particular batch of pellets. The next tin of pellets may group better at a different size. Granted, you may be able to experiment enough to find a nominal size that works pretty well across different batches of the same pellet or even across different makes and models, but it is unlikely to be optimal all the time. 

And by the way, size only the heads or use a tapered sizer. Skirts are deliberately a few thousandths larger to help establish a seal. Passing the whole pellet through a sizer will obviate this feature.

Steve,

While not an answer to your question, check out the TR Robb sizer's out of England. 

I recently ordered a .22 and a .20 and had a little fun playing with them. https://www.airgunnation.com/topic/20-jsb-exact-jumbo-heavies/

They're the tapered kind, so they preserve that ratio of skirt to head diameter that nervoustrig mentions. And they have an adjustable depth stop so one sizer can be used to size pellets into various increments, in the case that you're wanting to do a bunch of sizing and accuracy testing with goal of finding a correlate between head size and accuracy for a particular gun/barrel. 

Tried sizing in years past with only minor sucess. After much experimenting I found that if the skirt was slightly larger than the head, I gained a much greater improvement!! Even made a complicated little tool to control head size and slightly flair the skirt. It actually worked well but still had ocasional flyers. Started sorting by appearance and removing any obviously bad pellets and soon realized that sorting was much easier than trying to size each pellet!! Endvresult was still an ocasional flyer! I no longer compete, so a quick inspection and a beeswax lube and all is great, yes I still get an ocasional flyer....but with a lot less work!!!!