Go to the tags window. Scroll down and open the weapons tag. Then select magnum. In the dependencies window, after you select magnum, you should see a bunch of tags, click on the one that starts with "proj"(it should say proj/ magnum bullet or something like that.) in the 2 drop down boxes on the dependencies window, go to the one on the bottom. Then look for and click on the one that says rocket at the end. Click save changes, then resign with a map resigner and you're done.
