That's interesting. I should perhaps point out that I'm still using Z Langs from a batch which is about 20 years old, so that may well account for the difference compared to the ones which you have tested. The only downside in using this older stock is the dirty residue which they leave - there's certainly none of the 'clean burn' of contemporary RWS rimfire ammunition. Anyway, I'll soon be getting to the end of what I have and will need to look at alternatives, as my local dealer is only prepared to order Z Langs in batches of 5000 minimum!