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Thread: QB79 Ninja - The $200 PCP (PAL Required)

  1. #21
    Senior Member sholo's Avatar
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    I know it was only 20', but that is wicked accuracy using the stripper...

    I have no previous experience with airstrippers either, but my current project has one....hopefully I can replicate the results you had! If I get good results (even close to yours) I may fit a stripper to a few of my guns, at least the ones with a large enough bbl diameter.


    Cheers,
    Todd
    Todd

    Don't sweat the petty things, and don't pet the sweatty things!

  2. #22
    Moderator rsterne's Avatar
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    Anything over 1/2" can be fitted, the Hatsan strippers are threaded 1/2"-20 NF.... You could probably even thread a 12mm LW barrel that size, the threads would just be very shallow.... The back end is located on an O-ring to prevent it from unthreading.... Not sure if it would work, may try it some day....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

  3. #23
    Moderator rsterne's Avatar
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    I finished and installed the stock today....



    It's a Richard's Microfit Wildcat Thumbhome in Select Grade Black Walnut with Ebony Grip Cap.... beautiful figuring in the grain....



    I had to shorten the forearm and inlet it for the tank block and regulator.... The finish is 7 coats of Watco Danish Oil, each coat wet sanded, ending with a white Scothbrite pad of 1200 grit equivalent and then a coat of Dark Minwax.... The scope is a Leapers 3-9 x 32 AO with Sunshade.... The gun weighs 8 lb. 7 oz. as shown.... The Air Stripper is from a Hatsan PCP, I threaded the barrel 1/2"-20 NF to accept it....

    It's no longer a $200 PCP, however....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

  4. #24
    Moderator rsterne's Avatar
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    I made one more slight change today before the final testing.... The off center RVA screw was canting the cocking block slightly, and I noticed a slight scuff mark on the spring spacer.... I made a longer, one piece cocking block, with an integral spring guide and spring spacer.... The new cocking block is 1.25" long, of which 0.25" is a spring spacer that is 0.34" diameter, the other inch being full diameter to eliminate it canting in the tube.... That allowed me to shorten the RVA screw and just tidy things up a bit.... It shouldn't have changed the performance at all, but in fact I picked up about 10 fps, and gained a bit of efficiency as well.... The Preload numbers have changed, as I can't put quite as much preload on the spring at maximum with the shorter spacer.... Here is a new graph of Velocity and Efficiency vs. Preload using the JSB 15.9 gr. Exact Jumbos pellets....



    As per my usual practice, I selected a preload on the knee of the curve, just below the plateau, in this case 4.5 turns out.... I refilled the tank to 3000 psi and shot a string with the following results....



    I got 80 shots between 844 and 856 fps, an ES of just 12 fps (1.4%).... and was able to shoot down to 1100 psi before the velocity dropped below 840.... The average was 849 fps (25.5 FPE) at an efficiency of 1.21 FPE/CI.... During shooting the string, I shot 5 shot groups and sighted in the scope in my 20ft. indoor range.... By the time I was done, it was punching group after group in the same place on the target that were only 1/4" across, barely bigger than the pellet.... I can't wait to try this rifle out at longer ranges.... This is just about the perfect velocity to shoot the 15.9 gr. Exact at, putting it right in the middle of it's sweet spot for the Ballistics Coefficient....

    This has been an exciting project, and I'm extremely pleased with the final outcome....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

  5. #25
    Senior Member sholo's Avatar
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    Simply awesome...

    Love the stock! Nice work fitting it for the bottle/gauge

    Does the stock come already inletted for the QB, or did you do it yourself? Reason I ask is that I thought I read somewhere that they (Microfit) just do powderburner stocks.

    Whatever the case, she's a beauty!


    Cheers,
    Todd
    Todd

    Don't sweat the petty things, and don't pet the sweatty things!

  6. #26
    Moderator rsterne's Avatar
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    Richards only make one airgun stock, for the QB78, it is inletted for the main tube, trigger, stock mounting screw and barrel band, and fit well.... The outside of the stock, however was VERY rough and required a lot of sanding.... I was fortunate to be looking at a time when they had two QB stocks on their "Specials" page (not 2nds, returned or never picked up), both quite fancy pieces of wood.... This one had a deluxe buttpad, and ebony grip cap and forend (which I had to remove when I shortened it for the QB79....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

  7. #27
    Moderator rsterne's Avatar
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    I finally had a chance to do some testing outdoors today, so I tested all the pellets scoring "green" in the last tests indoors that I expected to have a decent BC at 25 yards.... I measured the average velocity at the muzzle and at 25 yards, for 5 shots with each pellet, and then used ChairGun3 to calculate the Ballistics Coefficient.... Here are the results....



    The groups were sorted as usual, with any group you could cover with a Dime scoring green, any group you couldn't cover with a Quarter scoring red, and in between no colour code.... I was surprised that all the JSBs were the only pellets that produced sub-dime sized groups.... and the best of those was the 15.9 gr. Exact Jumbo.... When you look at the JSB Exacts, the heavier the pellet the better the BC, as expected, and this results in a lot more FPE at 25 yards.... However, with the combinaton of good velocity and high BC, plus superb accuracy, I chose the 15.9 gr. as the pellet to use.... After sighting the rifle in 1/4" high at 25 yards, here is a typical 5-shot group....



    The small squares are 0.1", and the black squares are 0.4", so the C-T-C size of that group is less than 0.25".... I can get 70 shots per fill at 25 FPE, and basically it just keeps dumping them in a ragged hole at 25 yards.... I think we can call this project an unqualified success, and this rifle has earned a place on my "wall of keepers"....

    Bob
    Last edited by rsterne; Aug 23 2013 at 07:42 PM.
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

  8. #28
    Moderator rsterne's Avatar
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    Additional information, March 2015....

    Recently one of our GTA members, Ribbonstone, noticed a slight bulging of the end of the tube on his QB79, in the thin area adjacent to the screw holes for securing the tank block.... The gun was operated for a time at 1250 psi.... In response, I have done an analysis of the tank block attachment, which is detailed in this thread....

    http://www.gatewaytoairguns.org/GTA/...p?topic=105712.

    If you are building a QB79 HPA conversion of any kind, you should read that thread.... If you are using more pressure than the 1100 psi factory setting for a Ninja SHP regulator, I am now recommending that you pin the tank block with two additional 4mm or 8-32 screws, or a 5/32" shear pin, between the O-rings.... If you want to be more conservative, you might want to pin the block when using the SHP regulator.... or even with a standard 850 psi Paintball regulator.... Complete information is in that thread....

    Bob
    Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
    Airsonal: Too many to count!

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