Originally Posted by LibertyRadeon
Some pumps do have a detent system that functions to prevent rollouts, such as the Grey Ghost.
This is possible because a some Nelson-based pumps (Like the Ghost, Phantom, SL-68 II*) use an original Nelspot-style breech-drop style bolt, as opposed to the later bore-drop configuration used today by the Empire Trracer.
Apart from the detent issue, there are various advantages of each bolt shape such that debating which was better was one of the first mag/cocker-style debates in paintball lore.
*While the SL-68 II is breech-drop you can't fit it with non-barrel detents for various design reasons.