After spending the weekend with the Himes brothers I realized that pellet head sizing is critical to being accurate. If the head size is smaller than your barrel then it could go in at an angle relative to the barrel and come out the same way resulting in a pellet that is initially not flying straight. I could see this at 15 yards indoors. Unsorted would sometimes produce a 1-hole group but more often it would create a one-hole clover. At 15 yards it should be a single hole. And given sorted pellets at that point I could produce 1-hole groups all day long.
Next step is to figure out how to sort them. You have the Pellet Gauge which is about $50 but is very slow and a bit hard to use, or you have the Compellitor system from Mark Buchanan for about $370.
This second option is a bit pricey, but it is quicker and I think more accurate. I can do about 15 pellets a minute once I got the motions down. This requires a compressor generating 80psi or more and a reloading tool (about $30).
Setup is easy. Screw in the gauge at the top of the picture, put the die in the bottom and attach the pellet "seat" in the press. You then attach the air compressor, use the provided brass pellet to set it up and you're good to go. The directions provided have some typos, but nothing that prevents you from getting the gist. Below is a small video showing the operation. Currently I'm looking for pellets with a head size, according to the gauge, of between 29 and 36.
The Pellet Gauge will get the job done, but trying to get a 177 pellet straight up and down and not have the "die" shave anything off as you're trying this is just painful. It does work if you get the process down, but I would honestly need training because with my "large fingers" it is a long drawn out process.
In comparison in about 2 hours with the Compellitor gauge I was able to fill a tin with 500+ pellets that were of the size I was looking for after going through probably 1500 pellets.