Hi dog, hopefully i wont have to push it deep enough to need drain grooves :martial but hey, you live and learn.
I managed to get around to making a spike that will (hopefully) do the trick.
I have the older style RA single rubber muzzle. i see the newer ones have a piece of muzzle that sticks out on the bottem, so they would require a bit more work, like cutting a groove into the spike
Its made from aluminium, a section of 12mm bar, with the spike end lathed down to 8mm. The part that comes into contact with the barrel and muzzle has a curve milled into it so that it fits the barrel snugly. There are only two mods needed for the gun. one hole drilled into the muzzle. I drilled it into the rougher spot where they do the injection moulding. i also had to lengthen the shooting line a touch. I was a bit lucky because the loop that goes through the hole in the muzzle, to attach to the snap clip that goes to the shooting line was big enough to accomodate the spike. this is not the case with my buddy's RA. Now the snap clip lies down the side of the spike. I also need to source some longer screws that are made from the same non ferrous metal that the original screw is made from. at the moment i could only get steel screws and they need to be replaced asap.
two screws hold it in place, one in the muzzle, and one in the orignial muzzle barrel connection hole. the holes are counter sunk (drilled out a bit with a bigger drill bit) so they dont snag the shooting line.
it took me about 2 hrs to make, but then i had access to all the required machinery, and someone to drive it.
the tip of the spike is tricut made using a fixed disk sander.
I am doing the float test today, and i havent tried to shoot it. i hope they dont stress me taking my speargun to the varsity pool.
a double wrap may give hassles, but i dont see myself getting a double wrap any time soon.
the cool thing is if it doesnt work, ie it sinks, snags the shooting line or whatever, there is not real "damage" to the gun.
A picture would probably make a lot more sense, but no digi cam available just yet, so you will have to put up with my poor sketches.