Our nets were made by a fisherman who made nets for many of the operators in our area, just over the hill from you at Ohope Beach. Material used was white flat nylon cord that held its knots better than the round section and was more flexible so it draped over the deer better. Dyneema would likely be worth a try as it would be lighter and have less drag due to the smaller diameter of the cord for the same strength. Benefits would be less recoil as you could use lighter weights, higher velocity, greater range. Size of our nets was 3.6m (12 foot) square with 150mm (6") mesh to allow them to penetrate small openings and minimise opportunity to snag on vegetation causing them to pull off the animal prior to its neck and legs becoming entangled. Particularly small diameter high strength cord will increase the likelihood of cuts being inflicted, however a goat is typically a lot lighter than a deer and not as strong so maybe not a worry.
We used shotgun powder for propellant, Win 452AA or Win 700X; 30 gr of 452AA or 27 gr of 700X capped off with a small blob of silicone (elephant snot), in a high use situation crimps will cause the case necks to split. Don't try these loads in your guns right off, you may never go that far, the information is historical - like you'd get from a museum. Weights were 100mm of 18mm round bar with a chain link welded on one end to attach to the ties on each corner of the net, no o-rings just a small indentation in the base of each barrel above the splitter to retain them when you dropped them in.
Our net guns were of all steel construction built off Mauser action 308's and had a pistol grip only with a very wide opening trigger guard to save the meat on your fingers, and the bones as well. Barrels were likewise of steel but I have seen some, like yours, constructed of aluminium in later years. Your coupling looks like a CP or hydraulic coupling; I haven't had experience using one of these in this application and figure that it would probably be worth talking to someone that has experience prior to putting it to the test as there is a significant shock loading developed when your charge meets with around 0.8 kgs of stationary steel weights. Definitely wear gloves when firing and probably safety glasses until you are confident that you are not going to get any blowback. I've seen a lot of physical damage suffered by man and machine at the behest of net-guns. When loading the net into the canister lay the net out flat on the ground and remember to insert the bottom two weights in the canister first, the body of the net next and last the top weights so that it leaves the gun in the optimum pattern.
Your means of retaining the net in the canister was common in the South Island, most operators here used around 3 strips of masking tape applied horizontally and vertically across the face of the net and adhering to the canister to retain it. The tape was also handy when operating in areas where farmers were prone to becoming distracted from their normal farming routines, off duty Police officers were jealously guarding their pet hunting spots, and Forest Service (pre DOC) rangers ventured to uphold the law of the land, @
R93 probably gets the picture.
We only ever caught a half dozen or so goats; they were scarpering for the bush when we were miles away, got in close and they stuck their heads in the fern to "hide", my shooter jumped out, lifted their tails to check for value and proceeded to tie up the nannies. Some operators caught thousands as live capture of deer tapered off in the late eighties, for me the half dozen was enough - I figured that there had to be a more noble means of making a living than that. :)
