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Crossbows - Everything about Building, Modding, and Using your Crossbow Gear

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5 posters

    .44 Magnum Crossbow

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    CelticCrossbows
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    Post by CelticCrossbows Wed Feb 20, 2013 6:58 pm

    Hi,

    I have an idea for a pneumatic crossbow that I am considering building
    (and possibly producing). I just wanted to get some outside opinions on
    whether I should bother as the bow could definitely viewed as being
    overkill (quite literally).

    My idea is to use high pressure compressed air to drive an arm and
    pulleys forward and propel an heavyweight arrow to about 300fps. By
    heavyweight I mean a steel arrow weighing about 4000 - 5000 grains (a
    lot of typical crossbow bolts are around the 400 grain mark) which would
    yield about 1000 -1100 foot-pounds kinetic energy. This kinetic energy
    compares favourably to a .44 magnum (average 1180fpe).

    To compare with compound crossbow (Barnett Ghost 400) which shoots a 425
    grain bolt at 400 fps which yields 151fpe. That is about the same as a
    .22 lr bullet.

    My thinking process behind this bow is to provide people with an even
    more effective hunting bow. I don't know about the rest of you but if
    was going to be shot and eventually killed with a gun then I would much
    rather be shot with the .44 rather than the .22 and get it over and done
    with quickly and cleanly.

    A bonus of my design would be that you wouldn't have to cock it. Just load an arrow and the fire, easy!

    Also a solid steel arrow will me use a few little tricks to ensure a
    truly deadly projectile with a large wound path and serious knock down
    power.

    You should be able to get at least 4 full power steel arrow shots out of
    my design, followed by 14 half power aluminium arrows (1900 grains, 300
    fps, 380 fpe) and finally 10 carbon fibre arrows.

    Well, that's about it. Please let me know what you think. Is it overkill or an humane hunting bow?

    By the way, I am aware that there air rifles out there that shoot arrows
    but they seem mostly to concentrate on speed which is great for range
    and produce nice neat small holes though animals.
    Jason D
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    Post by Jason D Wed Feb 20, 2013 7:45 pm

    You are approaching this from the wrong angle, kinetic energy is not the best way to approximate a measurement of killing power with a crossbow or bow. What is most important is that you have a certain minimum weight/velocity/broadhead combination. The goal is to make a neat hole through the vitals that causes a fatal loss of blood in as short a time as possible. What you seem to be building here is more of a high powered airgun meets speargun hybrid. .44 Magnum Crossbow 874442478 It is neither fish nor fowl. Wound paths are wound paths with bolts or arrows, it will be a cut that matches the broadhead. What effect are you expecting?
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    Post by CelticCrossbows Wed Feb 20, 2013 10:21 pm

    Jason D:

    You are completely correct in what you say. I do have genuine concerns about whether the design would work significantly better than what is currently available.

    The whole idea was to use a larger broadhead than would be feasible with a lighter bolt and POSSIBLY include solid sharpened fletching to increase the size of the cut. Thereby increasing the likelihood and damage to vital organs. This could also increase the chance that a poorly placed shot would result in a kill rather than a wounded animal.

    I know now that using the .44 magnum as a comparison was a mistake as it confuses the issue. I wanted to grab people's attention and to give some idea of the difference in power I was proposing. Bad idea.

    The result I am hoping for is difference between a thrust to the chest from a broadsword and a rapier. Both of these can kill. The rapier could easily pierce a lung but the broadsword might take the heart with it as well. I just want to up the odds in my favour and minimise unnecessary suffering.

    I hope this is a bit clearer.

    Any questions or constructive comments are genuinely appreciated
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    Post by Jason D Thu Feb 21, 2013 12:01 am

    I now understand what you are trying to accomplish, a more humane kill is a worthy goal. I don't think that the way you are approaching it is the correct way however. Right now a properly tuned and matched archery or crossbow set-up will take any game on the planet with proper shot placement. No weapons system can make up for poor shot placement, a 180GR 30-06 has around 3100ft/lbs of energy at the muzzle, yet every year I know of moose, deer and elk that have run off after soaking up two, three and even four rounds that were poorly placed.
    Your idea of a larger broadhead is a good one, but it would have to be custom made, there is not a mechanical made that would stand up to that kind of KE and the largest commercial fixed broadheads aren't much over the 1-3/8" to 1-1/2" mark.
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    Post by JoergS Thu Feb 21, 2013 4:54 am

    While the idea of a bolt weighing more than 300 gramms, flying at 90 m/s is quite fascinating, I think your approach to achieve that is wrong.

    I have issues with the mechanism.

    A crossbow THAT powerful will have all kinds of problems. The string and pulleys will have to be super heavy duty, making them very heavy in weight, too. This means they will have a huge momentum and there will be a lot of friction, too.

    I think you best way to get to the result you are looking for is to directly employ the pressurized air for the shot. This will eliminate all of the mechanical issues, increasing the efficiency of the weapon by magnitudes.

    You can do that by shooting an unfletched bolt through a steel barrel, or by using a hollow (fletched) bolt with a massive tip that slides over a hollow steel tube. Think blowgun, or reversed blowgun.

    This would of course no longer be a crossbow. We are talking bolt shooting airgun.
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    Post by hullutiedemies Thu Feb 21, 2013 11:13 am

    JoergS wrote:You can do that by shooting an unfletched bolt through a steel barrel, or by using a hollow (fletched) bolt with a massive tip that slides over a hollow steel tube.
    Or just sabotted arrow and large caliber barrel.
    Eg. 50mm barrel with just 10atm mean pressure will make 2kN push. A half meter long barrel would have around 1kJ muzzle energy.
    WIth 10 bar you can use lightweight plastic or aluminum barrels and make a revolver with multiple rotating barrels ( not my invention , saw it years ago on "Pimp my Ride" or some similar show- newspaper launcher from a "paperboy-mobile" episode )


    Or take the pneumatic nail-gun approach. And simply have lightweight large diameter piston inside the device to kick a projectile.

    Mechanical transmission would make sense if you use the vacuum approach, though. Plus you would really get something like an air-spring engine that way.
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    Post by CelticCrossbows Thu Feb 21, 2013 6:22 pm

    JoergS wrote:While the idea of a bolt weighing more than 300 gramms, flying at 90 m/s is quite fascinating, I think your approach to achieve that is wrong.

    I have issues with the mechanism.

    A crossbow THAT powerful will have all kinds of problems. The string and pulleys will have to be super heavy duty, making them very heavy in weight, too. This means they will have a huge momentum and there will be a lot of friction, too.

    I think you best way to get to the result you are looking for is to directly employ the pressurized air for the shot. This will eliminate all of the mechanical issues, increasing the efficiency of the weapon by magnitudes.

    You can do that by shooting an unfletched bolt through a steel barrel, or by using a hollow (fletched) bolt with a massive tip that slides over a hollow steel tube. Think blowgun, or reversed blowgun.

    This would of course no longer be a crossbow. We are talking bolt shooting airgun.


    Thanks for your comment. I had wanted to keep the crossbow style in order to sneak this device into archery season but the more I think about and the more replies I get on other crossbow hunting forums, the less inclined I am to continue down that path.

    I had been tempted to use the design you mentioned before and may return to it having recieved other forum's feedback.
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    Post by CelticCrossbows Thu Feb 21, 2013 6:30 pm

    Nerd Flintstone wrote:
    JoergS wrote:You can do that by shooting an unfletched bolt through a steel barrel, or by using a hollow (fletched) bolt with a massive tip that slides over a hollow steel tube.
    Or just sabotted arrow and large caliber barrel.
    Eg. 50mm barrel with just 10atm mean pressure will make 2kN push. A half meter long barrel would have around 1kJ muzzle energy.
    WIth 10 bar you can use lightweight plastic or aluminum barrels and make a revolver with multiple rotating barrels ( not my invention , saw it years ago on "Pimp my Ride" or some similar show- newspaper launcher from a "paperboy-mobile" episode )


    Or take the pneumatic nail-gun approach. And simply have lightweight large diameter piston inside the device to kick a projectile.

    Mechanical transmission would make sense if you use the vacuum approach, though. Plus you would really get something like an air-spring engine that way.

    Thanks for your helpful comments. If I was to go down the airgun route then I would most likely use the sabotted arrow in a large caliber barrel. This would give me the large surface area to propel such a heavy projectile. The downside would be the large compressed air demand.

    I think I'll have to have a long think about things
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    Post by Hotspur Fri Feb 22, 2013 7:35 pm

    Jason D wrote:...the largest commercial fixed broadheads aren't much over the 1-3/8" to 1-1/2" mark.

    I got these mechanical heads to test this fall - 3" cut:

    http://reviews.cabelas.com/8815/419875/nap-f-o-c-crossbow-broadhead-reviews/reviews.htm

    If this thing opens up in your quarry its going down.
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    Post by Jason D Fri Feb 22, 2013 10:52 pm

    Yes, 3" would do it, I've heard mostly good things about the NAP mechanicals, but also a couple of reports of them not opening, nothing I have seen for myself. I am using heavy Zwickey two blades on my traditional crossbow and Rage three blade mechanicals with my Darton PRO3800. I haven't used either of them enough yet to come to a conclusion but so far so good.
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    Post by JoergS Sat Feb 23, 2013 12:39 am

    And I have just received six of these (SOG is a new sponsor of mine).

    Should make great tips for a monster size crossbow.

    http://www.sogknives.com/spirit-knife.html

    Sponsored content


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