I have used them, maybe 2 years ago in a Steyr. Indoors they were great, they weren't bad outdoors in a near windless day but in a strong wind they were terrible, terrible compared to 7.9 grain Express. They weren't designed for magazine use Pavel (JSB) made these for his target shooting hobby where single pellet loading is the order of the day.
My friend tried them in a Walther and had similar results. My son knows somebody that has used them effectively in a springer for HFT though and it's often windy at these places. It's likely to be things like air delivery and barrel twist rates that decide how effectively your gun uses them.