This video takes a Cooper T backspin bolt for a KP2. Known as the undershot bolt, produced by Chauncy Toombs of the company Cooper T. This bolt was made to fit the Sheridan KP2 rifle. These bolts are also known as undershot or low blow bolts, because they direct the air through the bottom portion of the bolt’s face and push the bottom of the ball forward causing the lift and backspin spin effect.
According to Sergey Levkov at LAPCO, these bolts and others which used the bottom bolt hole, added backspin to the ball by blasting the ball against the top of the barrel and rolling it. This added spin/roll on the ball would make the ball jump up when it exited the barrel.
Sergey implemented this idea on some of his early Autococker bolts (prior to machining for ANS) in the early 90s. Other manufacturers such as Alamo City Paintball and Jack Rice at Alien used this same bottom bolt cut.
Levkov writes, “Yes the back spin bolt works. [Using this bolt you are able to] get 80-90% of the performance of a flatline or Apex tip. The drawback was that the paint can’t handle the hit against the top side of the barrel and you have shoot at reduced velocity. Now in those days we were shooting at 300 so reduced velocity was 275-280 but way more range. It shoots pretty flat for the first 50-75 feet and then the ball start rising. It does the same thing as the flatline in that it rolls the ball against the top of the barrel to create back spin. We made .693 barrels for the back spin bolt and the Automag Zbody (automag body that looks like a micromag body but has a Airsoft style hop up pad at the top to back spin the ball).”