Look for the Technisub Ranger thread here, it includes this diagram.
I Have an Old (20 yrs) Technisub-Ranger , Pistol type, speargun. Needs seals for sure.... Can't find the old ones. I know tech support is No More, and I really need a Manual for a 'Parts Breakdown' picture to see if anything else is needed. I broke the piston but have a Lathe so thats no...
forums.deeperblue.com
I did find that thread and looked at that, but it doesn't make it any clearer to me how those two plastic assemblies come apart. It looks like there's a second pin through the inner barrel, behind the sear pivot pin. It also looks like there is a screw through the upper left of the outer grip casing, towards the back, and possilbly a corresponding boss on the inner grip assembly, that might be the threads for that screw. There's no visible screw that I can find, unless it's behind one of the metal badges glued to the grip casing. I didn't want to pry one off before looking for confirmation that it was the right thing to do.
The internals shown in that exploded diagram look significantly more complex than the shorty model I have, at least to my eye (I don't have the gun here in front of me). There are a few pins shown that I don't recognize from the partial dismantling so far, and quite a bit of stuff concentric to the inner barrel that I don't believe is in my gun.