Here’s a scan of a form letter sent out by Smart Parts to enquiries about Smart Parts rifled barrels in 1991. However they weren’t a rifled barrel in the traditional sense. There were no spiral grooves or lands in these barrels. Their claim to fame was the spiral drilling in each barrel (see last photo). Smart Parts claimed that these spiral vent holes reduced turbulence and imparted a gentle spin on the paintball.
I bought one of these first generation barrels for my PMI-3 at the time and was very pleased with it. Accuracy was greatly improved over stock with this barrel. Still I was always sceptical of the so called science included in the letter as to how it worked .
Mine had a muzzle brake fitted by Smart Parts (as can be seen in the photo) to meet minimum barrel length laws in place at that time in Victoria Australia.