ACS Bolt

An ACS bolt (also known as an anti-chop system) is a special type of bolt used in some Paintball markers. The purpose of the ACS bolt is to reduce the amount of chopping (when a paintball is pinched by the forward motion of the bolt, causing it to break) by using a system that detects when there is an obstruction in the chamber and brings the bolt back. Tippmann has a similar system on their model line called A.C.T., or "Anti-Chop Technology".