my spear gun made of stainless steel

I try to create this stainless steel spear gun and I try to figure out how this spear gun really worked and I made it. this spear gun during trial to shut a dry wood on distance and the spear running straight about 4 meters and I hit the wood. this spear is very durable and very strong and comfortable to use for me. this spear gun is for fishing purpose only when we go to the beach.