I was just going to say here, how good I've found Defiant .177 pellets made by Prometheus and saw this.
I ordered a 1000 .177 4.52 posted for £13. Enclosed free were about five other pots of a hundred each, of other pellet types and head sizes.
Bob at Defiant Bob/R that is, sent the free jobbies for me to give to my mates at the range to try. good PR I thought!!
Anyway, the 4.48, 4.50 (7.5 gr) were the same as my 4.52mm in both my HW springers, spot on!! Shooting apples at least 40 yards, depending how high up on the tree LOL all shot in the same hole or same apple at least Cookers LOL.. Well the smaller size did shoot a bit higher ,being a bit less tight in the barrel. Not the most scientific of test's but good enough for me. The Theoben much preferred the smaller two sizes, but the Defiant pellet skirt fitted in the HW barrels superbly, better infact than HW's own pellet I thought..
To be fair I didn't try them close up!! but for pistols, I know Bob recommends a different pellet type some of which he enclosed free.
I have tried to get my buddies at the range to club together to buy 12 boxes between us. No doing!! you can order a mix and match variety but I fancy these 4.50 head size as a good compromise. Or would be quite happy with the 4.52 which fit as snugly as the AA I tried. Other pellet brands that I could also find no difference in comparison were BLRG's, Accupell and Lazerdomes. Dare I say, not quite as good either in some cases..