Can I ask how long back this bad batch goes (if anyone knows) the reason I ask is I'm on holiday at the mo and can't check my barrel but I have the exact same problem with a new HW100 bought in January ....it was like shooting a shotgun.
The ONLY pellets I can get any sort of group with are RWS superfields in .177 more importantly 4.51 head size,the gun will not put any pellets in the same place and is totally unpredictable if I use 4.52,4.53 regardless of make
now hoping this could be the problem.