[s_forbes]

We've found that most of the variations in our shots come from ball placement on the mechanism. The balls are only sphere-ish; the fabric stitching has an impact on their shape. If your main contact point on the ball is in the middle of a square patch, vs the vertex of three square patches, the ball seems to react differently (and predictably).

A launching mechanism that is resistant to ball placement would likely fair best. I would expect the large flat-disc linear punchers to be more consistent.