Few today would have seen or even used a spring powered speargun, but in the early days of spearfishing as a recreational activity they were all the rage and the latest thing for the then new fad of going underwater and emerging, to the astonishment of beachgoers, with a fish.
Ever since Alexandre Kramarenko (a Russian émigré) and his partner Charles Henry Wilen (an American) introduced their compression spring gun in 1937/1938 the underwater world has come under assault by a growing variety of spearguns wielded by Europeans who had thought that this activity was only something practiced previously "in the islands" with simple spears. In the USA and elsewhere the growing availability of dive masks and fins also brought about a desire to shoot fish in their own environment and everyone scrambled to find bigger and better underwater hunting solutions.
The spring gun held sway as the most powerful of underwater arms until band rubber ceased being scraps scrounged from inner tire tubes and other forms of rubber goods pressed into service as "make-do" power bands.
The key to maintaining shooting performance from a spring gun was to maintain its efficiency, which it does not have much of to start with. The enemy of tube confined sliding coil springs is friction, and friction in the barrel tube is what robs spring guns of their power as the spring coils always slide on the alloy tubing wall. To limit these frictional losses the springs are heavily greased which makes them a magnet for every sand particle within reach of the gun. When a spring is strongly compressed it buckles in a series of kinks and these kinks rub on the barrel as the spring expands back to its non-compressed length. Many people think spring gun propulsion springs are greased to stop them rusting, that is true, but it is also to lower the friction encountered with the spring moving against the inner wall of the barrel.
In order to maintain shooting performance the grease had to be replaced frequently and if the gun hit a sandy bottom it definitely needed changing as grease embedded with sand skyrockets friction levels inside the barrel. Cleaning was a post-dive chore with numerous rags, a tub of grease, pliers and associated tools for extracting the long springs from the gun.
Here is how you can do it today, perhaps a little easier than the pioneers did it. The fixing bolt that secures the spring in the gun is removed, then the trigger is pulled to lower the sear tooth to stop it impeding the spring's removal from the barrel as the coils pull past the sear tooth position. The removed greasy spring is wound in a circle inside a large diameter plastic container like that used for large cakes or pastry products such as a family sized pie. Then either degreaser fluid or petrol is added (ultra caution is needed with petrol) and swirled around in the plastic container which will pick up the grease and dissolve it allowing all foreign particles to fall off the spring to the bottom of the container. The spring is then fished out and hung on a nail driven into a fence post at an angle so that the spring droops in a long curve at the top when depending downwards from the nail. Any remaining particles are wiped off with a clean (but soon to be dirty) rag and WD 40 is then sprayed on the spring and under gravity spirals its way down the spring to cover all the coils. Do this on a hot day and things will evaporate and dry off much sooner, plus you can pitch the cleaning solution on the ground (out of the plastic container) and it will evaporate in no time.
Now place a small wad of rag around a wooden dowel which is attached by a long nylon cord with a toggle at its front end and use this as a "pull through" device to clean out the inner barrel tube. A shot of petrol or degreaser ran down the inside of the barrel tube first will soften the deposits as you want them coming out without too much resistance on the movement of the rag covered dowel. You want the rag to have some loose clearance around the dowel when inside the barrel bore, so the dowel cannot be too fat in diameter or sand particles will scratch the inner barrel surface as the rag can then behave like sand paper and will be too tight to move along the barrel. A couple of passes with the "pull through" are needed with visual inspection looking along the bore of the tube with sunlight lighting up the appropriately angled barrel to see how clean it is all looking.
The springs can be regreased by painting them with warmed up grease with a small paint brush, or putting grease in your palm, or on a clean rag and pulling the spring through your closed hand, turning the spring coils as you go. At the end of this procedure you and the spring will be covered in grease. Long springs seem to have a mind of their own, so be prepared for the spring whipping around unexpectedly and administering grease to your clothing and anything else that it happens to touch.
Lastly feed the freshly greased spring back into the gun and refasten the attachment pin and then wipe the gun down to get rid of extra grease that has wiped off the spring exterior and is emerging out of the numerous anti-suction ports that pepper the barrel.
At the conclusion of this procedure you will realize why no one in their right mind still uses a spring gun, unless of course they love playing with mechanical items like old guns and can feel empathy with the generations long before who faced this greasy chore as an inevitable necessity.
Unfortunately even with the best spring guns power out is much less than power going in, especially as the internal bore of the barrel gradually roughs up and the springs get progressively rusty if you shirk on the regular and essential maintenance.
I have written this as a result of my recent greasy encounter with the springs from my Cressi-Sub "Saetta Extra" (the blue anodized tube was extra) and a "Freshman" spring gun from Japan. Needless to say I will not be shooting these guns any time soon! I had put this task off for months and figured that it was now or never, plus it was a hot and still day, you do not want dust or grit blowing around when dealing with greasy metal objects like long coil springs.