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Thread: tryed some new mod's on my QB79

  1. #1
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    tryed some new mod's on my QB79

    Well as you all know people with QB's put lots of cash in them,
    Well I'm no exeption I could have had a Hammerli AR20 brand new for about 150$ more then what I have in my QB79
    But I been doing the final tuning on my QB79 and Man I'm in love with it.

    bought a new Ninja 13ci 3000psi tank regulatet at 1500psi
    did some test and it was putting out 944fps to 3000psi tank full 850fps 1600psi not bad now the shoot count was 82 not too good.

    so I took my modded valve crazzy glue it and put it back in the QB79 now the Fun part.
    it put out 1054fps at full tank 3000psi and 1020fps at 1600psi now that is great my pellet keeped good grouping for all 75 shoots I got out.

    now I have a few deccision to take keep the modded valve or re instal the stock valve.
    I know the stock valve is reliable and like only 50 to 80 fps lower really not worth the problems I could get with the modded one.

    so this week end of tuning is not over. I'm going to clean this puppie and and polish it. make it perfect for the next FT
    I will cut my hammer spring 1 1/2 coils so I get more shoot counts and have to pump it less [ not that I mind pumping it ]
    I will ajust my scope at 50 yards and have a ton of fun doing it.

    TY Eric Love the new tank.

  2. #2
    Member Gippeto's Avatar
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    Spending a bunch of time and money on an inexpensive rifle is something I understand...there's not much "QB" left in my QB.

    You can gain a little more consistency out of the Ninja regulator if you polish the edges of the bellevilles where they contact one another. Doing this will alter the stack pre-compression and the reg will have to be re-adjusted. Use a thin smear of silicone grease on the contact points of the bellevilles.

    Another thing that helped improve consistency was polishing the inside of the tube where the striker runs, and spraying the striker with Jigaloo Graphite Extreme. It doesn't change viscosity with temperature...very consistent.

    Can you explain what exactly you "crazy glued" in the valve? Valve stem?

    Al

  3. #3
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    Yes the stem was lose on the valve so I used some crazzy glue to glue it so I could test the modded valve out.
    and it does work very well, but I'm afraid it will break on me in a FT comp. so I will re instal oem valve.

  4. #4
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    today I instaled new seals and polish clean and lube and cut one coil off my hammer spring.
    now the airgun is almost noiseless I tell you the firering pin makes has much noise the the air coming out.
    now the fun part, I shoot 40 pellets and the gauge almost did not move this is wonderful I lost some speed with this new hammer
    sping mod but it's still putting the pellets out at 748 to 758fps and I can live with that, it's stong enuff for FT and I'm sure I will do much more then
    100 shoots per fill.

    I will test it out for shoot count and keep you all posted.

  5. #5
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    Nice work. I think you might be better off with the modded valve.

    "it put out 1054fps at full tank 3000psi and 1020fps at 1600psi" and "75 shoots"

    I know the shot count is not huge but the consistency is great with the modded valve. With the lighter valve spring it looks good! Another thing to think about is you can lighten your striker instead of just cutting the valve spring. It might give similar results and less hammer bounce but then sometimes you need more spring pressure and that can be harder on the valve stem. Its all a balancing act.

    Iam about the same FPS as you only with co2 still. I was getting 775fps on 2 12g's @ 84F but de-tuned it as consistency was not there. Its now doing about 755fps down to 724 fps with 30 good shots. Thats with a HDD, lighter hammer spring fully modded valve, opened up barrel port etc. one of these days I will go HPA with it but I hate pumping and don't have one.

    Bruce

  6. #6
    I feel like a kid who just walked into the middle of a conversation and wants to say something relevant. I do not know QB's and don't pretend to have any answers.

    This comment by Bitterman/Bruce has me confused. "you can lighten your striker instead of just cutting the valve spring."

    I am in the process of setting up a bunch of spring tests for the 2240 and have nothing emperical to offer, but, theoretically would it not be just the opposite?

    Heavier hammer spring gives the affect of a lighter valve spring?
    Lighter hammer spring gives the affect of a heavier valve spring?

    Heavier valve spring gives the affect of a lighter hammer spring?
    Lighter valve spring gives the affect of a heavier hammer spring?

    Certainly someone out there has already crunched the numbers and has taken into account pressure variations and spring combinations!!! But, in general, the above seem like the most logical result.

    Art

  7. #7
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    Dooh I made a type.. should have said hammer spring instead of valve spring.

    A lighter striker will cause you to loose power due to the valve opening ofr a shorter period of time. Often to account for this lighter striker if the velocity drops too much you need to increase the hammer spring power by a different spring or shimming the existing spring. There are many ways to achieve the same thing but the right combination of these things can be helpful in increasing shot count. Its a balance and lots of trial and error.

    If the valve is open too long you actually wast error. Also hammer bounce will result in lost air for no gain.

    Bruce

  8. #8
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    Well today was the last day of tunning,
    got it to 750fps average and I did over 100 shoots and was still over 2000psi off a 13ci bottle.
    this thing is so quiet it unreal it's almost like I get missfires or running out of air.

    Thanks all for your tricks.

    I not crazzy about the speeds since I was up in the 1000fps but the shoot count I love
    before could not even make it too 70shoots now 70 is ezzy.
    and 750fps is still very good for FT and this airgun is my dedicated FT airgun till I get my Benjamin Discovery.

    only one mod left to do, paint the stock on it black to match the rest of the airgun.

  9. #9
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    So I was doing the final testing on my QB79 and I used a full tank from 3000psi too 1500psi at regulator presure.

    well it was shooting average of 760fps thats is good all shoots are close from start to end like max of 25fps I think that is very good.

    but you will not beleave how many full power shoot I got out of this.
    I set up out side with the F1 chrony and chronied in sets of 32 since that is the max my chrony will keep in memory.
    so I shoot and shoot and shoot some more and got a total of 272 full powered shoost and about 30 that started going down so [ OVER 300 SHOOTS ]
    that is 272 full power shoots of 760fps to me that is wonderful I was not even doing 70 before this mod, cutting the hammer spring
    was a great trick thanks for helping.

    I did lose over 250fps with this mod, but the shoot count make more then up for it.

  10. #10
    Moderator rsterne's Avatar
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    What weight pellets are you shooting 270 shots at 760 fps with?.... Is the tank only down to 1500 psi at the end of the 270?.... The reason I ask is that If you are using 7.9 gr. pellets, that is 10 FPE, times 270 shots, for a total of 2700 FPE from one fill.... You are using a 13 CI tank, and assuming a pressure drop of 1500 psi (3000 down to 1500) that is 1500 / 14.5 = 103 bar.... That means you are using 103 x 13 = 1345 cu.in. of air.... 2700 FPE from 1345 CI of air is OVER 2.00 FPE/CI, which while not impossible, is pretty much airgunning nirvana.... I have never heard of that efficiency being achieved in .177 before....

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

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