Another interesting post.
After a lot of batch testing indoors and outdoors over the last few years, and I have realised that my results are similar to Brians, although I have not used a chrono down range like Brian. It would seem that head size means virtually nothing and is not indication of actual size.This has been found by myself with some expensive engineering measuring gear and by Brian and a few others with the pellet gauges that can now be bought. Chrono readings seem to give some indication of consistency in weight from the tin as well, which is fairly common knowledge I suppose.
The guns that I have been using for testing are AAS400, S410 and two AA MPR's (one of which has scored a few high 50 scores and the other was Kieran Turners multi course clearing MPR) as well as my tight grouping EV2, and for the last year my Steyr LG110. I have found that a mega batch is very good in all my guns including the Steyr. A few batches shine more in the Steyr or EV2 but there is not much in it.
I have really struggled to find good batches of JSB exacts but have found at least four very good batches of Air Arms Fields.I have not yet tried tried any of this years JSB exacts though and after speaking to Brian it seems that they are well worth looking at.
I have found some very very good JSB express batches that really did put the tightest groups ever by me indoors, but the first time I used them outdoors in wind for a competition they just went loopy, and they seemed not to follow the wind but de stabilise and fly up down or wherever. I dont have any hard evidence as to why this happened but I actually wondered if the shorter 7.9's were less stable in wind (only speculation on my part).
Also, last year after spending a small fortune on some AA field Die 9's and 2's that both of MPR's absolutely loved and shot very flat with, I went out and bought my Steyr, it was only after, that I realised that the Steyr might not like the very expensive stock of die 9's and 2's and I might have to sell them to find something the Steyr liked, as I also thought every type of barrel is different. Luckily the Steyr loved the same pellets and flew just as flat right out to 45/55 yards. After checking quite a few other batches since I have found that they are either good in everything, or nothing. I didnt keep my HW100 long enough to find how different that was. I suppose the BSA barrels might have different results as well.
All of this is not very scientific, but it does appear a lot of findings from people in depth testing batches is coming to similar conclusions.