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The 40mm Pucklegun and modern materials

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  • The 40mm Pucklegun and modern materials

    Hang on everybody, here we go! Spent a number of days at the drawing board designing the 40mm rifled Puckle Gun. The original was about 35mm smoothbore and bronze. The Material and chamber size of the original was a limitation to the range and velocity of the projectile. With modern steel alloys i am sure I can build a gun that will definitely out perform the original. The barrel is a section of ww2 anti-aircraft cannon, and the pressure bearing parts will be made from heat treated 4130 alloy steel.
    Click image for larger version

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  • #2
    At the end of the project, there is a profound difference between spare parts and left over parts.

    Location: SF East Bay.


    • #3
      Somebody is going to have a LOT of fun!!


      • #4
        I am machining the receiver right now. The breech end has a larger diameter opening to match the step at the breech of barrel. This shoulder will lock the barrel in one direction and the inside diameter is turned a few thou. under so that i can shrink fit the receiver onto the barrel. While i could have located a piece of heavy walled dom tube for the receiver, i elected to machine out a solid bar of 4.25 dia. 4130 stock because it only cost $20 and at hand while the tube was far more costly and had to be shipped. Under the receiver tube is a bar of 1018 that has been machined to fit to the receiver’s radius with a shoulder at one end because i dont want to rely on shear strength of the weld alone to withstand the recoil forces. This block has also been drilled to hold the screw that supports the cylinder plate. The screw is an off the shelf 15 inch long, 1 1/2 diameter grade 8 bolt. Tensile strength 125000 psi. I am dealing with pressures around 65000 psi. Here is a mock-up of some of the parts at hand
        . Click image for larger version

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        • #5
          I'm guessing that you won't be building a cylinder set up for square bullets for use against Turks?
          David Kaiser
          “You can have peace. Or you can have freedom. Don't ever count on having both at once.”
          ― Robert A. Heinlein


          • #6
            I would make the first several test shots from behind heavy protective cover. 65,000 PSI is a lot more pressure in a 40mm than it is in a .308.
            Kansas City area


            • #7
              Originally posted by Toolguy View Post
              I would make the first several test shots from behind heavy protective cover. 65,000 PSI is a lot more pressure in a 40mm than it is in a .308.
              this is not my first rodeo. I have been building full scale artillery for 40 years. I build the guns to withstand smokeless powder pressures. So yes, lots of testing.
              As the design is proven historically for smoothbore at 35mm, i only have to consider the increase of pressure needed to engage the rifleing.
              I am not driving armor piercing projectiles. Just 3/4 pound zinc or aluminum, with pyrodex powder.


              • #8
                Sounds like fun. I would hate to see one of our guys get hurt, that's all.
                Kansas City area


                • #9
                  Oh yes, certainly! I do take your caution to heart. I am fortunate to still be able to muster all my digits, appendages, most of my organs, senses and many of my teeth, considering the life i have led. At this stage of my life i will not squander those on poor choices, poor design, and misuse of explosive energy.


                  • #10
                    Here are some pics of receiver tube that was turned from 4.25 In. solid 4130 hardened bar stock. Also one of the chambers being turned from 4140 heat treated 2.75 in. bar stock.
                    Click image for larger version

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                    • #11
                      Here are some photos of the receiver being machined to receive the trunnions which are turned from 4130 bar stock. Those flats on the receiver were counterbored and the trunnions had a stub turned to a press fit, and a chamfer at the base to give a good penetrating weld. Collars were then turned to slip over the trunnions. These collars will be radius milled to fit down on the receiver and welded to the receiver and to the trunnion.
                      Click image for larger version

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                      • #12
                        It being Sunday, which is a day of rest and spiritual maintenance for me, i decided to spend time in the toy shop. I worked on my 40mm Puckle Gun some more. The current phase is assembly of the receiver, which consists of the main body, a pair of trunnion stubs and re-enforcing collars for the trunnions.
                        i coped the collars to fit well against the radius of the receiver. I fired up the Tig welder and laid in some nice deep welds, making several passes and quenching between passes so as not to accumulate too much heat to the entire piece. After the collars were welded, i decided to fit the barrel to the receiver.
                        i had machined the barrel and receiver for a shrink fit. I began a slow saturation of heat, using temp sticks to track the temperature and a caliper to check the inside diameter. When the caliper showed .004 larger than my barrel’s breech diameter, i quickly extinguished the torch, grabbed the receiver by the trunnions(with gloved hands) and slid the receiver on to the barrel. It went on with a sliding ring sound without a hitch. I then quenched the whole thing in my quenching tub.
                        Click image for larger version

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                        • #13
                          This may be a duplication, but i want to give some reference to this project. In 1718 James Puckle invented his repeating rotating chamber cannon. I built a table top .57 caliber version of the gun with an updated ignition system. And now i am building a full scale variation.
                          Click image for larger version

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