I've just had chance to have a dabble on the chrono and the results are as follows. Again using the Prosport, five shots with each pellet.

JSB Exact Heavy - 10.34gr - 685fps - 10.78 ftlb


AA Diablo match - 8.02gr - 779fps - 10.81ftlb


AA Diablo Express - 7.87gr - 800fps - 11.19ftlb


AA Diablo Field - 8.44gr - 774fps - 11.23


I think for comparisons sake i'll do the same test with my S510 pcp to see the difference. I think this clearly shows that the lighter variety are indeed more efficient in the Prosport. Not that there's anything wrong with the heavier pellet and on a windy day well worth considering using them as they still made good power and were clinically accurate. I think on a day with virtually no wind the express would be superb, but as an all rounder it has to be the field diablos.