Before you ask advice on a gun, you need to tell us how you are diving and where. We already know you want to go for grouper. BTW, slip tip is a waste here...... go w/ one big flopper.... much better and you won't have the tear offs when you get a gun that is powerful enough to penetrate....
Let us know how tall you are, strength and price range. At that point, everyone will pipe in on what they love. Me, I am a fan of an enclosed track gun cause I am on scuba. I want to reload fast and have the option to freeshaft if I want to. I couldn't do this w/ a rail gun, hybrid or some semi enclosed systems. I don't want to "have" to wrap the line in order to shoot or swim with it. As for size, if you are going after grouper, 50" or better....... Wood......... start cheap and work you way up....... If money isn't the primary issue, let me know for some custom builders contact info......
As for the technique........ I am going to copy it from another thread that I posted it in...... don't want to retype it again......
Obviously my opinion but I think you definitely need to go a little bit larger on the gun.
As far as your questions about hunting, I don't mean to write a book, but...... see if any of this makes sense to you as a beginner.
My version of Spearing 101, this might help you with your mindset on spearing.
One of the primary reasons that fish "react" to you differently when you are carrying a speargun or not is --------"attraction / attention".
If the fish has your "attention", he knows that you have signaled him out from everyone else and that is the reason that he is going to shy away. The last thing a fish wants is to attract the attention of something bigger than them for fear of being eaten.
What a fish picks up on is your tells, movements, reactions, etc. You may not realize that you are giving him a "tell" like in poker, but you are. As soon as you look directly at him, "tell". If he moves hard left and you drop your left shoulder (like how a plane turns) or kick harder with your outside fin, "tell". As he is swimming away from you, he goes left, right, left, right, and do you know what you do? Left, Right, Left, Right just by how you kick your fins or change your body posture like a shark does his fins. The fish is testing you to see if you are focused on him!!!
The reason that people tell you to relax is so you are not so "focused". This in turn doesn't give off "direct intention" vibes, which CLASS, is what?--------TELLS!!! As you have figured out, this list could go on and on. For fish that are a little larger and skittish, come done from on top of them or try coming up from underneath depending on the species. Grouper will roll on their sides when you dive bomb them to get a good look at you and see what you are doing. SMACK!! Consider approaching on a 45 degree angle when trying to "chase a fish down". Don't make eye contact until the last second. Watch him out of the corner of your eye while aiming your gun in his general direction until the last second. "SMACK".
If you are following a fish that won't stop, if he keeps going, start making a commotion by stirring up sand, banging on a rock, whatever. Break a sea urchin up and let the smaller fish start feeding. The larger fish will stop running and come back to see what is going on. Try chumming to take the edge off of the fish that you are following after. A chum bag will bring in small fish, then bigger fish, you get the picture.
Freeze chum without water in chunks and throw it in your bug bag and dump it just off of the ledge or structure when you get down there. (if you use water, throw some oyster shells in to make it negative) Small bait fish will go nuts over it and watch all of the gags and everything else come in. try dropping the stuff about 10 yards off of the ledge in the sand. Pulls the bait off of the structure and gives you a chance to have all of the grouper funnel to the closest point on the structure in reality, herding the fish together for ya. Dropping it in the area you are going to dive and watch what comes around in under 5 minutes. This is the time for you to really pay attention to fish behavior........ You will start picking up little tips in no time at all.
Everyone has tips and advice, take it for what it is worth and please don't take it as me telling you how to do it. That isn't the intent, just a little food for thought.
One more thing I see with guys missing longer shots is usually not locking their elbow straight before shooting on a powerful gun. That or not picking a small spot on the fish as the target. If you look at the entire fish as the target, your chances of a solid hit drop in my opinion. Most of the time you will start hitting continuously high or low depending on the gun and your form.
Hope it helps and good Luck.
