Taken from Ultimate Spearfishing Magazine volume 4
The beautiful thing about this break-away system is that when the trigger is pulled, the shooting line is immediately released and nothing has to pull out of any holes or do any other complicated things that could cause it to get stuck onto your gun. It is breathtakingly simple, requires no permanent modifications to your gun and is super effective when targeting big game fish. This is the exact setup that we used so successfully in our recent trip to Madagascar and would have lost many guns if we hadn't of rigged our spears this way.
Put your shooting line through 1 end of a crimp and thread it through the end of your spear. Pull the line back through the empty side of the crimp so that a loop is formed with the hole in the spear running through the middle of it.
Ensure that the crimp is sitting halfway along the ridge where the spear is flattened to fit into the mechanism before you crimp it tight - this ensures that the line moves upwards from your trigger mechanism and never tangles when it is released.
Put the spear back into your gun and make 3 full wraps around the muzzle and the line release. Cut the shooting line so that it is about 3 and a half wraps long. Loop 1 end of a shooting line bungi (the one that you would normally use to attach your shooting line to your muzzle) to your line release and stretch it a bit so that it will pull all the shooting line taught when attached. Make a note of where the end of the bungi is when stretched as this is where you will need to put a crimp on the shooting line here.
Remove the bungi so that it is not under pressure and attach it to the shooting line with a constrictor knot (the same one you would use to hold a wishbone in the end of your rubbers - see pg 26 of USM volume 1) on the spear side of the crimp.
You can now stretch the bungi and put the end over the line release again so that the shooting line is under tension. You should be left with about half a wrap of shooting line that is poking off under your gun. Crimp a loop onto the end of this line (or put on a clip if preferred) so that you are able to attach your shooting line to the end of your float line. I personally like to keep this last section of shooting line quite long so that I can easily hold it away from my barrel with my left hand when tracking fish to ensure that when the line is released with the fish powering for the bottom, there is no loose line to snag onto the gun or anything else.