bill: I doubt it's a loaded cartridge. The dent in the side of the cartridge casing is caused by extraction from an automatic or semi-automatic firearm, which means that particular cartridge has been fired, and is therefor spent. I doubt they went through the trouble of reloading it.
Also, if this pen uses a standard ink cartridge, the shaft would have to extend through the primer hole (which would probably need to be drilled out).
Also, if this pen uses a standard ink cartridge, the shaft would have to extend through the primer hole (which would probably need to be drilled out).