Don,
Use Loc-Tite on those spearheads or you will keep loosing them no matter how tight you hand tight with two pliers. All spearheads with floppers will give the propeller effect and will turn loose, Ice Pick is one of the rare one that doesn't. Use blue one or non-permanent. As for me I use red-one : permanent , one that you need to burn to break.
I have plenty of shafts, so I change shaft+spearhead combo. My shooting line is 3 wraps instead of two cause all my Riffes are not standard anymore and I am more of a scuba set-up, when I use a float, all I need is to use the extension shooting line I made. So this way I do not need dedicated breakaway/float set up.
Becareful with ur powerhead cause if u miss a fish and it hits something solid like a rig piling, that's when it will be most dangerous........it will bounce back. At ur typical shaft launching speed of 50 miles per hour, I don't think any spring will be strong enough to prevent a premature fire caused by water drag. If it is strong, in most cases it will might not fire upon impact unless u hit something as hard as the gills. Accidents have known to happened.
Anyway it is good to trade stories...fun.
If you ever managed to get the auto-discharge float on the gun, I would hate to see the MT-5 damaged from hitting the rig pillings. Most importantly make sure what ever line/string connected to the C02 firing mechanism and attached to ur wrist ............is something that will break or release under your own strength. This CO2 firing line/string might drag you as the fish drag the gun or if there is a horizontal piling in between your running fish and ur ascending gun, the fish can't run, ur gun can't make it to the surface and your wrist still caught on the gun ......at 20 feet .....how ??? Knife is one thing but in breath hold mode, you do not have the luxury of time consuming mistake.
Any float with CO2 inflation that can give 30 lbs of floatation, let alone 50 lbs ( say at 30 feet ) is not something you want to hold on to by accident, I personaly think it is a lethal thing. What if u get dragged and ascend so fast and hit your head to one of the piling ? Being in open reef or blue water is another story but when stuctures are like the rigs.............Hmmmm.....becareful Don.
When lines/string are so tightened on your hand by some 30 lbs of force wanting to shoot up to the surface, you do not need accidental loop or a nice knot to get into trouble of entanglement.......a wrong routing of line on your wrist is already bad enough. Make sure you dry test on land what kind of line/string can puncture the C02 steel nipple and your own hand can break it too without a knife.
Surprisingly a mono of 200 lbs can just snap a 30 lbs line when used as shooting line and dragged hard by the fish but if I ask you to break/snap that with your two bare hands, I don't think you can ever do it.
The guys reccomend a float line like the Riffes cause it is so thick and slippery, so less entanglement danger to spearos.
Whatever design u come up with , all of us are available to help you to think of the possible danger it might do to you.
Secondy, then we figure out how effective it will be.......cause in most cases we probably have tried it. You will be surprised at what kind of experiments people in this forum have been thru in the name of "progress".
Anyway dive safe.
IYA