Hi,
I emailed Bob Rothery the guy who now makes Wasp pellets, as some of the 5.6mm pellets measured only 5.3mm,this was part of his reply. Dear Sir

We are sorry to hear you are unhappy with one of our products.

We are at a loss to understand how you can have 5.3mm pellets! As you can imagine we sell millions of these pellets across the country and if a batch had somehow been made in 5.3mm we would have an epidemic of power and inaccuracy claims such as yours. Yours is the only complaint we have at this time