There isn't much stock that can be removed from a Shocker body. In a lot of cases, the body is too thin to work with, unless you want to add some surface cuts to the current milling pattern. I've seen some pretty cool work floating around on the internet forums from other custom airsmiths, but I never bothered to do much custom Shocker milling myself.
There's a few basic things you can do. First is the classic "SL miling", which involves removing a larger portion of the body from the sections surrounding the fire chamber. Material can also be removed from the front section of the bolt sleeve housing. The body below was surely the first custom-milled Shocker body out there, from back in 2004. I designed it for a customer and it was milled by Logic paintball who was doing airsmithing at the time.
The milling style proved to be unstable, though. With so much of the body removed, it had the tendancy to bent itself into a very slight banana shape (you could tell when you sat the body on a flat tabletop). When the frame was mounted to the bottom, it would pull the body into a straight shape like it was supposed to be. The body would leak when pressurized if the frame wasn't installed.
The point is this. It's not a good idea to remove this much material from the body. At the very least make a round edge shape to the bottom of the cuts; doing so should help relieve the corners and keep them from losing their shape as easily. In the months after this milling job I repeated it myself but altered the design a bit to help prevent it from losing its shape.
Here's another example of the SL milling that I believe to be the second milled Shocker out there.
I did spend a few minutes toying around with some ideas and used the Shocker body for reference. Some of these aren't very viable, but at least it was something. These were made back in 2003-2004 so my skill with modeling was a little different in those days.
Helical milling:
My most popular milling idea was ironically the most basic one. It consists of multiple helices wrapped around a barebones "shell" encasing the internals. Although simple to model, the design would be very expensive to machine in reality since it would require at minimum a 4th axis machine to produce (definitely not impossible though since many marker bodies are already made on 4th axis machinery). I also included cutouts for the fire chamber and bolt sleeve. The last picture shows my first attempt to create the milling shape, which was made using the stock body as a basis, however my version of Inventor at the time couldn't handle the modeling.
Flow milling:
Somebody posted this picture (below) on an internet forum as a possible milling idea. I took the picture and spent a few minutes trying to make it more detailed, but didn't spend much time on it. It was a simple body using Sweeps for detail. I liked the original picture since it has a somewhat organic look (the milling looks like tree leaves to me) so I estimate with further detail this could be turned into a very nice looking marker. oh well...
Razorback milling:
I designed this body while trying to achieve a "chrystal" look at first. However, the chrystal look quickly begun to morph into something different, which is what you see below. I believe it instead resembles a rock formation instead of chrystaline. The body is a reasonably intricate combination of sweeps mixed together. Although this body looks impressive, there is a problem with it....the back spikes would be deadly if you were to trip and fall onto the marker. For that reason a more blunted shape would need to be created instead. Click here for a short video showing the milling.
These pictures below include a very slight "perspective" to give the body a more realistic shape...
