If i save a animated weapon as .mb and open it again all my joints (J_Gun, Tag_clip and all) have the -mb name before the joints how can i disable it??

For most common uses I don't see why this would be needed. Most exporters account for this or the information is gathered from the user.

Regardless if it is a requirement a simple google search might have done some good:
http://www.fuse-design.org/blog/tutorials-cg/maya-remove-namespace-after-import