JC - you are right that the pattern is actually a three dimensional "sausage." If the target were stationary, then the 2 dimensional "holes" would a fairly exact indication. However, a moving target will move within the pattern. That means we would need to analize 3 dimensional "tunnels" within the pattern to be exact. That isn't going to happen in my lifetime - far as I can see. So, we are stuck with "patchiness" as a surigate for "tunnelishness." Ron Forsyth (Australian pest control pigeon shooter) did a lot of work on loads that reduced patchiness (per O & T) and found that there was some correlation to field shooting (of which he did a lot).
t1958 - you describe a test for point of impact vs point of aim. This is a useful test, but yields no data on the performance of the actual pattern. Useful pattern data must look at individual pellet strikes in some fashion. The "calibrated eyeball" is the simplest method and, of course, the least precise. Digital photos that can be compared and viewed by numerous "calibrated eyeballs" is a good step up. Counting holes inside a circle of some diameter at some known distance is the next step up. It is labor intensive and gives only rudimentary information. Measuring "patchiness" for a pattern is also a step up, but also is rudimentary in information. The cutting edge of the art currently is Dr. Jones's computer analysis of digital photos of patterns. This method is work intensive, but holds the prospect of real quality data; I'm still working on technique, but firmly believe it will be worth doing in the future.
I find it highly frustrating that there is not data to definitively answer the simple question that launched this thread. As noted, the data needed to get answers to this one, and several other simple ones, is massive. I plan to work on it in retirement and hope several others will join in an effort with common tools and techniques to create data that can be combined.
