I think it's because all these replicas use some kind of magazine that has to revolve to index each pellet and so a lot of co2 is lost on every shot as the fit between magazine and breach is not that good.The skiff has a bit more whack due to the inline mag,but that brings its own problems pf erratic feed.For the price they are as good as can be expected,pay 3 or 4 times as much and things improve somewhat.