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Thread: Powerhead Advice

  1. #1
    Throbbing Member Dorkus's Avatar
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    Powerhead Advice

    Ok guys I need design help,

    I am sick to death of getting harassed by sharks when spearfishing. Over the last 10yrs I have seen sharks become increasingly aggressive and less intimidated by spearfishermen, often taking fish from spears and/or harassing divers until they get out. I am certain it is a learned behaviour and the bastards have gone unchecked for too long. I want to help them unlearn.

    I have seen a simple powerhead design used in the islands that I want to replicate and make a few of for me and some mates. The design consists of two sections of copper pipe of different diameters. A 357 round sits in the smaller pipe with the case rim resting on the lip, that sits inside the larger pipe on some sort of lip (I haven't worked that bit out, perhaps solder?). A rubber insert sits behind the round (inside the bigger pipe) and holds the tip of the spear aligned in the centre of the larger pipe so that when the device hits its target the momentum of the spear activates the primer and makes a nice little hole in the shark.

    That's the basic concept - Issues I have are where and how do I get the exactly right sized pipes? How do I insert a lip of some description inside the front of the larger pipe for the small pipe to sit on? Then I somehow need the exactly right rubber insert to hold the spear securely and stop the round falling out the back.

    Is 357 a readily available and appropriate sized bang - Needs to kill a good sized shark without blowing me up (noting I'm in the water and probably about 2m from the business end).

    Thoughts?
    (other than "why would you want to kill sharks?" or "don't kill sharks" - there are too many and they are starting to be arseholes. I don't want to cull them to the point of ecosystem collapse, but I do want to be able to get in the water an good spots without the almost certainty of losing fish to sharks)
    “The society that separates its scholars from its warriors will have its thinking done by cowards and its fighting by fools.” - Thucydides 463BC

  2. #2
    Throbbing Member Dorkus's Avatar
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    kinda letting this

    Sent from my SM-G930F using Tapatalk
    Tommy and takbok like this.
    “The society that separates its scholars from its warriors will have its thinking done by cowards and its fighting by fools.” - Thucydides 463BC

  3. #3
    Bah, humbug ! Frogfeatures's Avatar
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    Random thought, what effect will water have on the ammo, or is the whole thing, other than the ‘open end’ waterproof ?
    Found this on youtube, any help ?
    https://youtu.be/nDVPmtq1_d4
    He nui to ngaromanga, he iti to putanga.

    You depart with mighty boasts, but you come back having done little.
    Sounds like a typical hunting trip !

  4. #4
    Almost literate. veitnamcam's Avatar
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    Copper tube?
    It is less strong than the brass case containing all that pressure in the cartridge and that case is designed to be contained by a steel chamber.

    S/S may be a better option.
    "Hunting and fishing" fucking over licenced firearms owners since ages ago.

  5. #5
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    Quote Originally Posted by veitnamcam View Post
    Copper tube?
    It is less strong than the brass case containing all that pressure in the cartridge and that case is designed to be contained by a steel chamber.

    S/S may be a better option.
    Or does being underwater help support the case?
    I think a mythbusters episode is needed here.

    found this one stainless steel like @veitnamcam suggested but def not home made
    https://www.youtube.com/watch?v=RalxSZtPm-U
    the one from the video-not cheap
    http://www.billsbangsticks.com/

    This one is though-didn't watch much just bits and pieces

    https://www.youtube.com/watch?v=LJPhCKd-Gy0
    Last edited by csmiffy; 26-11-2018 at 07:39 PM.

  6. #6
    Almost literate. veitnamcam's Avatar
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    Quote Originally Posted by csmiffy View Post
    Or does being underwater help support the case?
    I think a mythbusters episode is needed here.
    found this one stainless steel like @veitnamcam suggested but def not home made
    https://www.youtube.com/watch?v=RalxSZtPm-U
    It would help support the case I guess but provide a lot more resistance( and hence pressure) in front of the projectile.....38 special with its lower loading may be a better option?
    "Hunting and fishing" fucking over licenced firearms owners since ages ago.

  7. #7
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    Found this. One on their suggested using something like an automatic center punch for a firing mechanism, although I would've thought that would take a bit too much effort

    www.HomeGunsmith.com Static Archive

    Maybe find an old rooted 303 barrel to start with. Drill out to suit the cartridge. If the action was completely toast you could braze/tig a sleeve to hold all the bits together and use that to anchor to the spear, although that would be a bit heavy
    needs more thought that one
    Last edited by csmiffy; 26-11-2018 at 07:47 PM.

  8. #8
    Throbbing Member Dorkus's Avatar
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    Quote Originally Posted by veitnamcam View Post
    Copper tube?
    It is less strong than the brass case containing all that pressure in the cartridge and that case is designed to be contained by a steel chamber.

    S/S may be a better option.
    It was definitely copper but I imagine that was more to do with it being cheap and able to be sourced locally rather than being the ideal material.

    I think SS is a much better option
    “The society that separates its scholars from its warriors will have its thinking done by cowards and its fighting by fools.” - Thucydides 463BC

  9. #9
    Member viper's Avatar
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    Quote Originally Posted by Dorkus View Post
    Ok guys I need design help,

    I am sick to death of getting harassed by sharks when spearfishing. Over the last 10yrs I have seen sharks become increasingly aggressive and less intimidated by spearfishermen, often taking fish from spears and/or harassing divers until they get out. I am certain it is a learned behaviour and the bastards have gone unchecked for too long. I want to help them unlearn.

    I have seen a simple powerhead design used in the islands that I want to replicate and make a few of for me and some mates. The design consists of two sections of copper pipe of different diameters. A 357 round sits in the smaller pipe with the case rim resting on the lip, that sits inside the larger pipe on some sort of lip (I haven't worked that bit out, perhaps solder?). A rubber insert sits behind the round (inside the bigger pipe) and holds the tip of the spear aligned in the centre of the larger pipe so that when the device hits its target the momentum of the spear activates the primer and makes a nice little hole in the shark.

    That's the basic concept - Issues I have are where and how do I get the exactly right sized pipes? How do I insert a lip of some description inside the front of the larger pipe for the small pipe to sit on? Then I somehow need the exactly right rubber insert to hold the spear securely and stop the round falling out the back.

    Is 357 a readily available and appropriate sized bang - Needs to kill a good sized shark without blowing me up (noting I'm in the water and probably about 2m from the business end).

    Thoughts?
    (other than "why would you want to kill sharks?" or "don't kill sharks" - there are too many and they are starting to be arseholes. I don't want to cull them to the point of ecosystem collapse, but I do want to be able to get in the water an good spots without the almost certainty of losing fish to sharks)
    Hi Dorkus,
    I am an old time spearo with probably 25 yrs under my belt and a lot of fish. I have dived up Mangawhai a lot especially Te arai reef where I shot a ton a Kingies, snapper and John Dory. Awesome spot.
    I 100% agree that sharks and in particular Bronzies have become very bold and cause some very scary and exciting moments.
    Down in the BOP they are no better with some particularly aggressive fuckers in Western bay at Mayor Island.
    Once you pull the trigger it's like ringing the dinner bell and some of these boys are big units to be in the water with when food is amping them up.

    As far as power heads go there were some commercially available a few years back. See if you can get hold of Darren Sheilds at Wettie in Auckland or try Wild Blue. They may know where some are available.
    If you can find a old copy of Ben Cropps spearfishing book I think he may have had a power head design in there.
    He talked a lot about using a 303 or a 12 gauge shell. I know some guys have also used 44 mags.
    You will need to choose your shot as the fuckers have a small brain and are tough. I did hear you have to be careful as you can rupture an ear drum.
    Do not test on rocks as I read a story of a guy who tested his power head on one and the shaft bounced back on firing into the rock and impaled him.

    As for any do gooders that tell you you need to respect them tell them to go fuck themselves. I doubt any have been in the situation you have experienced.
    I've had some very hairy moments so if you get the power head up and going shoot some of those pricks for me .......tell them Viper says Hi .

  10. #10
    Member viper's Avatar
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    Ohh, and yes the ammo will need sealing, nail polish works well.

  11. #11
    Throbbing Member Dorkus's Avatar
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    Quote Originally Posted by csmiffy View Post
    Or does being underwater help support the case?
    I think a mythbusters episode is needed here.

    found this one stainless steel like @veitnamcam suggested but def not home made
    https://www.youtube.com/watch?v=RalxSZtPm-U
    the one from the video-not cheap
    Welcome to Bill's Bangsticks - manufactured by Caddo Machined, LLC

    This one is though-didn't watch much just bits and pieces

    https://www.youtube.com/watch?v=LJPhCKd-Gy0
    Yeah the idea is to do it cheap so I can give them away and encourage a couple of mates to do their bit.

    That homemade one looks like it would work provided I can find the right diameter tube and rubber hose insert - I never thought of gluing the round into a snug fitting tube...
    The guy seems like he is on some pretty good drugs but his video made sense and I reckon the design is simple enough.
    “The society that separates its scholars from its warriors will have its thinking done by cowards and its fighting by fools.” - Thucydides 463BC

  12. #12
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    I had one 20 odd years ago, used a 44 mag round and was machined aluminum, similar to your drawing but with a spring to keep spare tip of primer, tried it out on a stump and goose, and a couple sharks, a good tool, but worthy of a healthy does of respect, and caution, don't be firing at any hard objects or geese.
    Dorkus, outlander and dannyb like this.

  13. #13
    Member Tommy's Avatar
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    Would a 410 be a good alternative?
    Identify your target beyond all doubt

  14. #14
    Throbbing Member Dorkus's Avatar
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    And for anyone who thinks sharks haven't learned they can tune in to Prime now for the move "Deep Blue Sea" then you will know why I want powerheads.
    “The society that separates its scholars from its warriors will have its thinking done by cowards and its fighting by fools.” - Thucydides 463BC

  15. #15
    Sending it Gibo's Avatar
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    If you have to kill sharks mate take up another hobby. Its not on
    kiwijames, 7mmwsm and systolic like this.

 

 

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