I have one of Ray Odor's .223 PPD. Someone posted the link to the site above. I definitely recommend it. Very easy to use and very very effective. I just keep it up my wetsuit sleeve until I need it and then you can get it out quick and slip it onto the shaft. Check out the "killspike" on the website also. Very nice for when you have your spear out and are not prepared for Mr. Grey Suit. BOOM!!!
Dryglove:You can buy some special stuff to seal the primer and bullet head or just use finger nail poilish.