Upon first hearing the miracles of the JAM bolt, I was curious to see what all the hype was about. I did a little research and the concept of the chopless bolt was interesting to me. I made the gigantic price tag and received my bolt in a few days. I installed it with no problems and adjusted my ram for the perfect fit. I have to admit, the JAM bolt does take away the dead space in the chamber to prevent secondary paintballs from entering into the breach, but that is where the perfection stops. After the required thousand shot break in, I experienced ball breakage in the breach at least one per hopper. In fact, I thought it might be the hopper, but after switching from a Angry Halo to an Egg then to a gravity feed the results were the same. What was happening was blowback was going into the feedtube causing balls to break. The breaks were with such force that they would splatter the inside of my hoppers.
The problem is when the bolt slams forward and stops on a half fed ball, the built up air has to be expelled some where. It appears that expelled air is discharged up into the feed tube at such velocity that breaks due and will occurr.
I must admit the invention of the JAM bolt is an interesting concept, but the actual application leaves much to be desired.
Some people have had great luck with this bolt and some haven't. I have owned a DEZigns bolt made by Robert Hernandez for the past two months. In that time, I have had ZERO problems with his open faced bolt and detents. As much as the JAM bolts are for what you get I would recommend something else.