The Zero B in my opinion is the best of the three factory boards released by Planet Eclipse. That board is basically identical to the E2 boards, I believe they released the Zero B as an upgrade for the people who have purchased the E1 and would like to upgrade to the E2 without spending an arm and a leg for a frame when they were relatively new. The E1's from past experience loved to suck up batteries, but still have plenty of features to fine tune, however the Zero B/E2s were a lot more user friendly and better on battery consumption.
From pics provided of the bolt, it looked like he was simply trying to take off mass to reduce weight. Guess he was trying to make the bolt a lot lighter by removing material in hopes of making the marker cycle faster. But again I'm sure this can be debatable.
As for finding a new Karnivor style bolt, it's going to be tough. It's unique in length, the Karnivor's won't accept standard pre 2k/2k+ or even p block style bolts. Hopefully someone on here will have an insight on where to purchase them new but I have yet to see any aftermarket or OEM bolts that are new floating around.
In order to take off the Karnivor style back block. You must first disassemble the internal cocking system:
1.) Remove frame, beavertail, and bolt.
2.) Unscrew the internal cocking rod that's attached inside of the back block. Best to use a small crescent wrench, note that the ICS (internal cocking system) rod is most likely loctited into the back of the back block.
3.) The back block will now be able to unscrew from the pump arm like a standard Autococker.
4.) You can now remove the IVG, if he does have the OEM style IVG then it's best to invest in the proper Karni IVG tool for later use. (http://www.paintballgateway.com/wgpstokaauiv.html
) But for now you can simply find pliers or use two allen keys and just unscrew it out.
5.) Once that's out, Main spring should slide right out, onto of the Karnvors body should be a hole that's big enough for a 1/8th allen, slot that allen key down until you hit the Hammer's lug, adjust counter-clockwise while inspecting the lug nut from the bottom of the body until the lug is flushed into the hammer's body. That will now slide out along with the ICS which is attached to it.
5.) If you wish to proceed to taking out the valve, you'll need a valve removal tool (http://www.paintballgateway.com/chitauvajamn.html)
. The operations of removing the valve assembly is identical to any other standard autococker in the market.
The Karnivor's beavertail, beavertail screw, and IVG works correspondingly. Make sure you note that when installing the beavertail's screw, it must slot between the fangs of the Karnivor's IVG. Otherwise you'll just end up snapping one of it's fangs off. The screw will set between the slot, acting as a stopper so the IVG won't unscrew while firing. I believe the screw for the IVG is a 10-32x3/8th (http://www.paintballgateway.com/scbuhe10x3821.html
) someone please correct me if I'm wrong.
If you truly wish to tinker and fine tune your marker, the madman spring kit provides excellent spring combinations, but I've honestly found the stock Karnivor internals to be flawless.
But for $280? Heck, that's a great a pick up considering they went over a grand when they were first introduced!