Someone please correct me if I'm wrong, but I do believe the only difference between the two is just what you pointed out, one is semi-only, and the other has select fire.
As for what should you get to upgrade it?
At least a barrel system and HPA to start.
A barrel system such as a Freak, or a Pipe kit would work just fine.
As for HPA, anything with a high output pressure would be just fine as well. I would suggest a 68ci 4500 psi tank.
Then I would most likely upgrade the ram and LPR with an eclipse ram and Palmer Micro rock LPR (I'm not sure if they still make them, or you can find them.)
If any of my information is out or date or incorrect would someone please let me know, as I have been out of the Autococker scene for quite some time. Thanks
