Very interesting. A long range accurate rifle with fast rate of fire like the Enfield would be a great help against pirates. That along with a couple of shotguns. The key element is the ability and willingness to use such weapons. Probably only a few sailors have either.
While anything is possible, most of us here have enough supplies to see us through a year or more of very bad times. Though it might make you feel better, its a mistake to try to attribute what you plan for yourself to the rest of us. The life of a travelling hobo/pirate might seem romantic but can only lead to death. Its the last resort for the rest of us.
Heck, put a .50BMG on board. No way the bad guys would get close enough to be worrisome. Matter of fact, I know a guy who has done just that on his boat. Of course, bring some greasing money if you are going to foreign ports so they look the other way.
This topic has been covered elsewhere, and the biggest problem is entering foreign ports with different gun laws than ours. A enfeild wouldnt draw much attention, nor would a stainless steel 12ga, if stowed in a locking cabinet, but a SKS would be harder to explain. Most of the areas mentioned in the articles are unsettled and unpoliced by civilezed nations, leaving You on your own. A enfeild or two would be very useful at longer ranges but how do you determine who to target?, and at what range?. Most of these "Pitrates" are stealing from the rich, and sometmes these stolen boats are used as "Grasshoppers" running drugs into our ports until the boat attracts attention enough to warrant scuttleing her. The crews on these stolen vessels are dumped when they take over, and then they go about running the buisness of drugs.