First try at a roller gun

    I've been wanting to try a roller gun for a while, but I thought it would be interesting to adapt some of the stock parts I had on hand, instead of building a gun from scratch. So I made up a Delrin and stainless muzzle, and will try the two stainless buttons at the rear to secure the bands. The quick and dirty slide ring was just my simple way to use an existing shaft, because the shooting line couldn't run to the shark tab without likely fouling on the wishbone arrestor pegs. This isn't intended as a long range gun, so I'm hoping the affect on accuracy will be minimal.


    I chose the peg arrangement because I wanted the bands to stop before they got pulled part way around the roller and affected the spear trajectory. I'm a little worried that the pins will be a weak point, but I did use heat treated 416 SS dowel pins, which are about twice as strong as 316. Also, I don't plan to use a lot of preload, so hopefully the force on the pins will me manageable.


    I thought overall that the design made for an intersting approach, because it could be a "bolt on" mod for anyone who had the same barrel and a shark fin shaft.


    The gun is 42" overall, which should be about right for the dirty water I'll use it in. Grouper is closed here, and Snapper will be in another month, so this will be for those quick little mangroves on the shallow wrecks.

    Interesting. Have you tried shooting it yet? I am not sure if the band will catch the pegs after shooting it. Keep us posted please.

    Quote from Dan

    What's stopping the rubbers from popping off the rollers?


    Hopefully, the wishbone snags on the two arresting pins while there is still enough preload on the bands to keep it from jumping off the rollers. If need be, I can extend the metal sides to wrap around the front and capture the bands. I elected not to do that at first to keep the weight down.


    Quote from japsw

    pardon my ignorance but what is the benefit in a roller style gun compared to a standard band gun?


    A little more power in the same length, or a little shorter length for the same power, without adding additional bands.

    Edited once, last by Guest ().

    I think there is also less muzzle jump. When I shoot my little rollergun it just recoils straight backward. I shot some close up nigh speed video of it and the video shows the gun just pushing straight backward out of the frame- no upward movement at all. I think it's also more than a "little" more powerful than a conventional gun of equal size- like maybe 50- 75% more, depending on preload.


    Can't wait to see it shoot (and shoot it)! :D maybe we could do some target penetration tests and see just how much more powerful it is. compared to the gun rigged the conventional way- food for thought.

    They are super powerful. They pull bands in-line (less muzzle lift=less loss of power) and much longer band pull than normal band guns.

    I had a chance to test fire this a few times in Wood Guy's test tank today, and I learned a few things:


    1. Wood Guy's high speed camera is freakin' COOL for this kind of stuff!
    2. The roller gun design works nicely. It was easier than expected to load, the wishbone arresting pins worked well, and I had no issues with the bands jumping off the roller.
    3. This gun has surprising power compared to a standard band setup. One of the advantages to this build was that I could easily replace the roller muzzle with a standard muzzle and a single band with the same stretch ratio.


    In Wood Guy's tank, we were shooting at a foam archery target that's about 12" thick. With the standard muzzle, my shots were hitting about 4" low (10' to the target) and penetrating about 7-1/2" into the foam target.


    With the roller muzzle, the shots were dead on vertically, and protruded 4"-5" through the back side of the foam target. I like this setup a lot, and I am excited to tinker with it more. I think it would have plenty of power for what I want to do, even if I shorten it a bit more from the current 42" length.


    Wood Guy shot some really nice video of both the roller and standard muzzle, which shows the shaft moving forward with measured marks in the background to calculate shaft speed. He'll post it as soon as he has it ready.

    Tin Man congrats, thas a very nice roller set up:thumbsup2:, keep the info coming;).


    Are you planing to do some business with these?.


    Regards.

    Sadot Hernàndez.


    Success, albeit clumsily! :thumbsup2: I made it: Film the video with new hs camera > download to new computer > edit video with computer software > Get u tube account > upload video to u tube > download video to forum. This makes building spearguns look easy!


    This is a shot of Jeff's new rollergun muzzle as the gun is being fired. The pin(s) you see sticking up are the "arresting pins" that grab the wishbone as it nears the end of the barrel. It was shot at 1000 frames per second, then most of the time was edited out. More to follow. The process is clumsy right now, but after some tweaking with the camera set up, and some improved operator skills, this is going to be one awesome anylitical tool.


    YouTube - ‪Jeff's Rollergun Muzzle Shot‬‏

    Already zoomed out as much as possible. Need a wider test tank. :D


    I think I need to crop more before the "good" part. Even though it's only a second or two, it seems like an eternity at 1000 frames per second. Baby steps!

    Great!!


    The video is fantastic. Very, very interesting.
    I will do many tests with my rollerguns in a big tank too, about speed, penetration, etc.
    I hope show the test here in a few weeks :)
    By the moment, i have only real-tests with fish :D. You can see them in the blog (www.rollerguns.com)
    I have used rollerguns (only) the last three-four years, and now i don´t want other spearguns.
    GreekDiver is right, "They are super powerful". And less backward movement, and lighter, etc, etc.
    I have rg 80cms, 90 cms, with 7-7,5mm shafts. The power is fantastic.
    I have too other rg 110cms, 120cms, 130cms.. with 8 mm shafts. The power... incredible.
    The best of all: Super powerful with a load in kgs very comfortable.
    I think, Tin Man is yet a new fan of rollerguns forever :thumbsup2:



    Javi.

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