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Thread: Beefing up an armex mk2 tomcat pistol

  1. #1
    Join Date
    Jul 2012
    Location
    Chesterfield England
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    124

    Default Beefing up an armex mk2 tomcat pistol

    After reading Hamish`s thread in search for more bolt speed on his 175lb rifle I decided to have a go of increasing the speed on my little hand held poelang made pistol by adding an extra 80lb limb rather than increasing the stroke which looks a lot of hard work making the bits .

    I cut the ends off a spare limb so it would clear the nocks on the old limb . Drilled a couple of 6mm holes and made a couple of little ptfe pads to dampen any noise between the 2 limbs and work as sliders . The stroke was increased by what ever the thickness of the limb was .

    Took about 10 minutes to mod the extra limb .

    I chrono`d my pistol when I first got it and got around 180 fps shooting 106.5 grain aluminium bolts. which gave 7.65ftlb of power.

    After adding the extra limb it now shot the 106.5 grin bolts at 235 fps for a power of 13 ftlb

    It shoots really flat out to 20 yrds now so I`m very pleased . 20 plus shots through it so far and nothing has broken . I might mod the cut limb a touch more at the ends as it looks like over time the edge might damage the string at the loop serving . But then again I might not as strings are cheap and it shoots great so I can live with decreased string life for the extra power gained .








  2. #2
    Join Date
    May 2013
    Location
    Scotland
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    37

    Default

    Mental !!! I love it Now, where did I put that spare 150lbs prod.... ?

    Hamish

  3. #3
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    Jul 2012
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    Chesterfield England
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    Default

    Its all your fault Hamish lol .

    I think a 175 and a 150 limb would be slightly over the top . You would be able to get a bolt to land in my garden from yours

    Maybe 2 x 120lb prods would work ? and loose some of the extra draw length ? Bet it would be a bitch to string and cock though.

    I`ll rattle a lot more shots through my pistol and post back if anything fails . There is no trigger mechanism on the pistols though so I think the only thing that could go wrong is kill the cocking arms as its pretty tough to cock now compared to before . Great fun though .

  4. #4
    Join Date
    Oct 2013
    Location
    United States
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    15

    Default

    I bought an NC Star fishing cross bow off Amazon. It came with a compound limb. It was a rattly piece of junk. It is listed as a 90 lb draw. I say bunk on that. More like 35 lb. I replaced the compound limb with an 80 lb fiberglass prod. I also put some heat shrink on the fingers of the cocking device to help quit it from rattling. But I did that after the video. I have no chronograph so no way of knowing speeds. But I do know that the original configuration would sink the plastic arrows that came with it about an inch deep into a target I made out of 8 layers of corrugated cardboard taped tightly together. With the fiber glass limb they went in about an inch to an inch and a half deeper.

    I'm thinking about picking up another prod to see how it would perform doubled up like this.

    Crap, just looked at the NC Star, there isn't enough room in the slot for two prods

    https://www.youtube.com/watch?v=bZ0XUud5Ug0
    Last edited by Broke Winger; 11-06-2013 at 01:20 PM.

  5. #5
    Join Date
    Nov 2013
    Location
    Oregon
    Posts
    8

    Default More details please

    Hey nutshot, I'm doing some similar (and more, other) mods to my 80lb Cobra. But, I'm pretty new at this and don't get some of what you did:

    What are the 6mm holes for (2 of them)?
    Are the ptfe pads glued on or otherwise attached, or stay in place due to pressure between the limbs? What are they commonly sold as (where can I get them)?
    Are the two limbs held together in any way other than pressure?
    Is the cocking manageable? (I extended the cocking lever with a M4 style "buffer tube" to which I can now mount a stock, but it was mostly for greater leverage).

    Have you done more tests? How's it holding together?

    Thanks!

  6. #6
    Join Date
    Jul 2012
    Location
    Chesterfield England
    Posts
    124

    Default

    Hi 0theories,

    the 2 holes are to hold the ptfe pads . The pads are shaped like a top hat and driven into the holes ether end of the limb.
    With 2 limbs stacked there was a very fine gap between the limbs so the pads just fill that void and stop the limbs clattering together. The pads I made on my lathe. I`m not sure if you could buy something similar off the shelf but maybe some rubber grommets would do or even cut some small strips of rubber like inner tube and glue them on the modded limb .

    The limbs are just led in place with the pressure of the standard limb bolt .

    Cocking pressure has increased quite a bit but I find it more than easy enough to do. Fitting the string was also a lot harder but I bent both limbs by hand and got a helper to pop the string on without too much stress.

    Everything is still lasting fine since the mod .
    I`m thinking of putting an m4 stock on mine too . More for extra stability than leverage . Longer distance accuracy has increased massively with the extra bolt speed.

    Get some pics up of your stock . Would be interesting to see your adapter The only thing putting me off fitting a stock is it might look too home done going from a round stock tube to an oval cocking stirrup. I have a spare stirrup though so I can always bin it if it looks to ugly .

  7. #7
    Join Date
    Aug 2013
    Location
    Canada
    Posts
    170

    Default

    I would be affraid of damaging the string release mechanism with that extra pull on it.

    Other than that, great job!
    Carbon Express Covert SLS
    4x32 Glass-Etched Reticle Lighted Scope
    Maxima Hunter 20" Crossbolts with 2" Rage Chisel tips and green launchpad lighted nocks

  8. #8
    Join Date
    Jul 2012
    Location
    Chesterfield England
    Posts
    124

    Default

    There isn`t really a trigger mechanism on this pistol Radikal.

    The string hooks into the body of the crossbow and the trigger is just a rising ramp that dislodges the string from the hook.

    The extra tension is held on the aluminium frame so chance of failure there is pretty much nil. I wouldn`t try this with the plastic body versions though as I`m sure that would be bound to fail .
    The only thing that might not last as long is the cocking arms but so far they seam fine.

  9. #9
    Join Date
    Aug 2013
    Location
    Canada
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    Default

    Oh... ok, well in that case i would just worry about the string being stong enough.
    Carbon Express Covert SLS
    4x32 Glass-Etched Reticle Lighted Scope
    Maxima Hunter 20" Crossbolts with 2" Rage Chisel tips and green launchpad lighted nocks

  10. #10
    Join Date
    Jul 2012
    Location
    Chesterfield England
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    Default

    Standard string seams fine too . Not been changed since I posted this thread and it had had some use before mods

    If you did want to fit a beefier string the string off a few variants of compound rifle are thicker/ stronger and will fit, pse copperhead , poelang CR-034BA , armex marauder or mk-250 Same length just thicker.

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