I had no trouble scoring 553/600 in three competitions, using RWS Diablolo Basic in two of them, Pardini competition pellets in the third. That's as high as I made it in pistol competitions before injuring a shoulder while working out with weights. Can still shoot 540, using whatever pellet is handy, and mostly shoot H&N Finale Match as I bought quite a few of those. But Diabolo Basics have been shown by a number of tests (look around on targettalk, especially for posts by 'Rover') to be within 1% of the accuracy of high-end pellets like the R10. Considering the vast price difference it seems not to make sense to go for the fancy pellets unless one is at or at least very close to Olympic level as a competitor. A 1mm difference in group size at 10 metres isn't even close to as significant as the typical 15mm or more difference between a casual pistol shooter and a top level shooter.