How to rig a speargun with mono
The mono on a speargun is one of the most overlooked maintenance jobs by the average diver. I constantly see divers with ratty, cut, frayed and nicked mono on their guns. This may be fine for shooting a few bream and smaller reef fish but when you go to take that shot on a big jewie, kingfish, mackerel or wahoo you’re going to wish you had changed your mono. For me personally I change my mono if it gets any sort of nick or cut. If a particular fish during the day runs me around some reef I’ll make a mental note to change that mono. It doesn’t take much for a big fish to trash your mono. One particular rock hop I had just put new mono on the spear and speared a kingfish of 14kg on sand. No damage done to the mono at all however I ran into the school again over some rocky reef and after shooting another 14kg fish and landing him my mono was worse for wear. So much so it was the one time I was wishing I didn’t run into a jewie or cobia, I would have been hesitant to try my luck with mono that had shreds coming off it. Another spot mono wears a lot is the hole in the back of spears, it is essential to make sure these holes are smooth and burr free.
Now we know why its important to change your mono out regularly and check it for signs of wear how do we go about doing this? With some spear fishing retailers charging $15 to put a new mono on a speargun it makes sense to do it yourself. These are the basic tools & materials I use to put mono on a speargun. Pictured are mono (duh!), crimps, crimping tool, lighter, scissors and a speargun waiting for new mono.
As for the mono I use 1.80mm stuff as I find it fits in mechanisms better than the 2.0mm variety and doesn’t affect the flight of the spear as much either. For this mono I use 2.2mm crimps (also sold as 2mm crimps in dive shops). Brand is debatable but I have been having great success with Shibahira brand. Other popular brands are Shogun and Jinkai.
I use double barrel copper crimps as they are very strong and in my opinion hold the mono better than a single sleeve crimp such as the aluminium variety. You can also use your copper crimps on stainless cable for slip tips ect but you can’t use aluminium as it will corrode out.
As for the crimping tool make sure you get a double actuated type not a single actuated like a pair of pliers. A good set will cost around $50-$90 depending on where you shop. I use a pair of Hi-Seas brand and they work great for me. Steer clear of tools where the jaws do not line up correctly as they will deform the crimp. Omer brand crimpers are notorious for this and are green in colour and sometimes sold under the Hi-Seas brand in dive shops so be sure to check the origin before buying up.
Getting started. I tend to uncoil a few metres of mono from the roll rather than cutting a piece off because this means no wastage (even though it is cheap). We start by threading a crimp into the mono and inserting it through the spear. I personally rig all my guns over the left of the muzzle, just how I have done but most people will go over the right hand side of the muzzle. If your going over the left hand like myself you will thread the mono through the left hand side of the spear so the mono sits nicely and runs up that side of the gun and doesn’t cross over. If you run your mono over the right hand side simply thread the mono through the right hand side of the spear first.
I use a lighter to burn a little blob of mono on the end. This prevents crimp pull throughs and makes it easier to adjust the position of the crimp prior to crimping.
I adjust the loop size so the crimp sits on the flat part of the spear so it goes through the muzzle with ease. Make sure your loop isn’t too long or it will sit over the notch in the spear and make it a pain to load the bridle into the notch.
Now using the appropriate hole size on the crimping tool you start the crimping in the middle of the crimp like so. Make sure you squeeze it good and proper.
Next we move out to the ends but not all the way. Leave approximately 1.5mm from the end uncrimped. If you crimp right on the end it pinches the mono and if the crimp does slip it will get shredded very fast, if a crimp slips and its got the ends flared out it won’t shred and you will still land the fish with any luck.
So now you have the mono neatly crimped to the spear.
Put the spear into the gun to check how it all fits. It should slide into the mechanism with ease.
As I mentioned earlier I run the mono to the left of the gun on the left hand side of the muzzle like so.
Run this back down to the line release and up to the clip on the front of the gun.
Make sure the mono is firm but not over tight as mono shrinks in water. Nylon is porous and absorbs the salt water which dries and the salt is crystallised into the nylon which makes it expand in width which shortens it. With the other end of the mono form a small loop about 1cm from the end of the clip whilst holding the mono on the gun firm. This extra 1cm distance will have the mono at the proper tension and will alleviate the need for bungies or shock absorbers. With an open muzzle gun I would recommend perhaps 2cm for a slightly tighter shooting line.
Now cut the mono loop with enough room to fit a crimp into the mono.
After threading and burning the end of the mono on the crimp you will have an uncrimped loop like so.
This is where you double check the distance from the clip on the muzzle to the loop on the mono.
Adjust it to the right place and crimp it like before starting in the centre of the crimp and then crimping the outsides leaving 1.5mm distance from the ends uncrimped.
All that’s left to do now is take the mono off the shooting line and attach it to the clip on the muzzle and you’re done! Here’s one I prepared earlier
Out of interest if you have a gun that will only ever be rigged with a pranger you can do away with the clip on the front of the gun and crimp the mono directly to the muzzle. Just one less thing to worry about because you don’t need to unclip the mono to thread a spear through the fish because the pranger won’t (shouldn’t) fire all the way through the fish.
So there it is. The initial outlay to buy a proper crimping tool, mono & some crimps might be around $100 give or take depending on where you shop but at $15 a pop to change mono you will be more willing to change it out and no go for a dive with mono that ‘will do for today’ and get a whole lot more value for money.