I stuck in all internals and found out a normal cylinder head and nozzle will work, the differences are quite small. Even with a CA hopup unit, new internals, and a modified magwell to work with the standard hopup it would only feed while upside down. I just ordered a Prometheus barrel, hopup unit, and a CA G36/M4 magwell so hopefully I can get it working.
SystemA PTW's have their own pros and cons and are not problem free (occasional problems with rain or water, bad motors, chopping BB's to powder, piston heads falling off the pistons, and a few others.) Generally they are for people who want realism above all else since on a performance per dollar scale its not a great deal. They are awesome guns in terms of regular airsoft guns but you can get just as good for a lot less if you aren't interested in the realism.
I am fully expecting PTW fanboys to pop in now and tell me how wrong I am, but meh. And yes I have owned a PTW.
If you are looking for a G36 the Classic Army version is the best in my opinion but I have never owned an ARES/STAR one but have heard good things. If you have a local gun doc they should have some recommendations for a setup that is reliable and at the fps level you want and can do the work for a small-ish fee usually.
Last edited by LUTNIT; March 13th, 2010 at 00:19..