This is funny.
If any of the oldtimers remember the Crosman Spotmarker from way back late 80's those were .50 cal. The Spotmarker revolver was basically the bb CO2 revolver that you can still get at Can Tire with a 6" barrel and drum bored for .50 cal paintballs. If this catches on I can see those old things coming back out for use. Hmm... now that I think about it I think those blowgun paintball doohickeys also use .50 cal.