Most guns of good quality shoot a wide variety of good quality ammunition adequately well.

Sometimes, you will find a belter that shoots a significant number of good projectiles very well. You keep those ones.

Sometimes, you find a gun that shoots very well with only one or two types. Those are “pellet fussy”.

It happens. It isn’t always down to the barrel, other factors are involved: bedding, harmonics, start pressures, etc, etc.

But quite often, it does appear to be the barrel. You isolate or modify as many as possible of the other factors, and nothing changes.

Jepho: your points are well taken, but I fear you overrate the consistency of barrel production in airguns. Or most firearms for that matter. The vast majority of civilian guns are built down to a price.

There’s no doubt that (e.g.) LW make good barrels, but most airgun barrels are not at that level, and HW100s have definitely in the recent past had issues with poor quality ones. A near-perfect barrel (e.g. for CF benchrest or military sniping) costs anything from £200-300. No air gun maker will spend that. Well, maybe for really high-end Olympic match stuff, but not for anything less.

Bottom line: sometimes you get a lemon.