I highly recommend you only allow an experienced machinist work on your paintball marker. This procedure is intended to get your marker ready to accept the Do-it-Yourself Half-block kits sold by White Wolf Airsmithing, though I‘m told that other half block parts will work with this guide as well. In this guide I am using a Bridgeport mill to do the machining. You may find other tools that you can use to do this conversion. Regardless of the tools you use, the dimensions are the most important part of this conversion. All dimensions are +/- .005”.
First, I recommend you rough out the upper portion of your marker with a bandsaw. Allow yourself at least ¼” for finishing on both cuts.
Place the body on a set of parallels in the vice. I recommend lining the vice jaws with paper to prevent scratching the body. Be careful not to over tighten the vice and damage the body. Cut the marker to the dimension shown on the print. WD40 is a great cutting fluid for aluminum. Use it liberally. It will give you a great finish and will prevent galling. Don’t try to take all of the remaining material off at once. Always sneak up on the dimensions by taking small cuts. You can’t put metal back on once it is gone. It is usually easier to get the thickness of the lower tube right first, then stay at that height and go over and cut off the back of the remaining portion of the upper tube. On most guns with a thru-body window the bottom of the window is already at the proper dimension. All you have to do is cut off the very back portion even with the bottom of the window. The GX5 done in this guide was done this way.
Your final measurements should be 3.200” from the front of the breech to the back of the upper tube and .900” from the bottom of the body to the top of the bottom tube. Keep these dimensions +/- .005”. If you go to far under the .900” dimension you will expose the IVG threads.
Using a scale, mark off the slot for the bolt pin to enter into the lower tube. You want the first mark to be .250” back from the end of the upper tube, then the next mark to be 1.250” farther back from the first mark. Make sure it is centered on the body. These dimensions can be found on the print as well. These aren’t too critical, just don’t stray too far from the dimensions given.
Find the center of the marker then plunge a ¼” end mill into the center of the lower tube and cut to your scribed marks. Keep the end mill and the slot wet with WD40. If you left your valve in be careful not to go to far into the lower tube. If you do, you may hit your valve stem when cutting to the .250” mark. You want the total slot length to be 1.250”. Don’t let the end mill sit still if possible. It will chatter and leave an ugly finish on the slot.
De-burr all places where you removed material using files or sandpaper. Make sure to get any burrs from the inside of the upper tube. If you don’t, you could scratch up the first bolt you put in. When you are done de-burring, clean the gun thoroughly. I usually wash it in hot water with dish soap then blow it out with an air hose.
Install the halfblock components and reassemble the marker as usual. Time it as you would any cocker.
If you choose to mill your own hammer, use a 1/4" end mill and just make a slot in the top .150 deep and .725 long starting at the front of the hammer. I recommend using carbide for this. Some hammers are hardened. I haven’t seen one yet that carbide couldn’t cut. I have seen a few that were very hard on HSS tooling.
Original JCM Guide Print...