Groupings of 60' at 75'? You'd be better off without a barrel!
Be more specific, what is the diameter of the spread of a measured number of bb's on a flat target at a range of 75'?
For instance; 15 G&G .20g bb's, on full auto, @ 400 FPS, outside, little to no wind, range of 50', and a spread of 4" in diameter (yes, that was from my P-90). Or, "about 30 rounds at about 75' and a spread of about 3' with TSD .25g bb's.