In the early nineties one of the most popular upgrades you could make to your paintball marker was an aftermarket barrel. The two most popular types at the time were the Smart Parts spiral drilled and the J&J straight rifled barrels.
But what set the J&J barrel apart from the crowd was its straight rifling. These all brass barrels had 4 lands set ninety degrees apart that ran down the inside of the barrel in a straight line. It was claimed that this would prevent paintballs from gaining a spin that might cause them to curve when they left the barrel.
Now I’m a bit skeptical if the rifling actually worked as advertised but J&J barrels certainly performed better than most of the stock barrels of the period. This can be seen in their popularity with many of the top players of the day.
The ones in the photo are for several popular markers of the era. The top one is for a Nelson style pump and is fitted with a copper sleeve where the pump arm sits. The second from the top is for a Sheridan PMI-3 / VM68 semi auto. The third is for an AutoMag and the last is a nickel plated brass barrel for a Kingman Spyder. The rifling is difficult to photograph but you can see one of the raised lands in the close up photo.
Interestingly, J&J are still in business today selling a range of ceramic coated aluminium barrels.