Good tuning results?

Forums PCP Airguns Good tuning results?

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    mcdonama
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    I finally broke down and purchased a tank (a Great White with all the trimmings from Joe B) and having a source besides the Hill pump has enabled me to do some tuning on my AA200T (.177).

    The 200T shoots about 575fps out-of-the-box with it’s most accurate pellet (H&N Match 8.18 gr) according to my chrony which is a Combro.  Admittedly, it’s inexpensive as chronys go and I have not compared it with any others accuracy-wise, but it does work ok and once I figured out how best to place it on the end of the barrel it rarely gives an err reading.

    In addition to changing the hammer spring and transfer port choke screw settings, I added a Huma External type regulator to the pressure cylinder.  With current settings, the rifle shoots a bit over 700fps for about 9 ft lbs of energy.  I could go a good bit higher especially with an air source like the Great White, but I only have about 30 yards available to shoot, I don’t hunt or ‘pest’ with it, and it also matches nicely with my springer’ power level (a Rob Hawkins tuned HW35 with Macarri spring).

    After a couple of shot strings, I’m wondering if the results I’m getting might be considered a good outcome.  Here’s a summary:

    190 bar fill
    57 shots before it’s off the reg
    avg 711.5 fps
    es avg about 12.5 fps (first string 9; second string 16)
    sd 4.95 fps (had to check this twice as, amazingly, it was exactly 4.95 for each string!)
    off reg at little over 100 bar (maybe 105 ish)

    I notice that if I throw out the first several shots (starts a bit high) as well as the last few, limiting the string to more like 50 shots, the ES would drop a little and the SD would tighten a little.

    Topped with a SWFA SS10x42, this is a very accurate rifle producing sub half inch groups at 30 yards.  No aspirin tablet is safe in my backyard!

    So, is this a good result or should I be hoping for lower ES and SD?  What do you think?

     

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    JoeWayneRhea
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    Sounds like really good numbers to me . I’d be more than happy with those . My personal opinion , I think sometimes guys get a little Too wrapped up in these numbers .
    For sure you want as much consistency as possible but if the POI is showing no change then a very small deviation in a shot string doesn’t mean much.
    I’ve been blessed enough to own a couple of absolute one hole rifles . The first I never measured , the second was simply the most accurate rifle I’ve ever owned . It showed ES numbers nowhere near what yours is , and at 50 yards it was one hole the size of a dime .

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    John_in_Ma
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    How much ai does the tube hold, 190cc, 200cc, 150cc? My S500 has a 231cc tube and will give me 170 shots on reg from 3000-1500psi with a bit tighter spread and deviation. If course i did extensive hammer lightening, played with a half dozen hammer springs as well as different size shims for the valve spring. Oh and the huma reg is set for 110bar.

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    JohnL57
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    I’d say you’re doing good-the s200 seems to be a really efficient platform as well as accurate.
    Here’s a link to a tuning thread-
    http://www.network54.com/Forum/79537/message/1469920007/not+a+%26quot%3BHunter%26quot%3B..just+%26quot%3Bregular%26quot%3B+AA+200%27s

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    mcdonama
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    “JoeWayneRhea”Sounds like really good numbers to me . I’d be more than happy with those . My personal opinion , I think sometimes guys get a little Too wrapped up in these numbers .
    For sure you want as much consistency as possible but if the POI is showing no change then a very small deviation in a shot string doesn’t mean much.
    I’ve been blessed enough to own a couple of absolute one hole rifles . The first I never measured , the second was simply the most accurate rifle I’ve ever owned . It showed ES numbers nowhere near what yours is , and at 50 yards it was one hole the size of a dime .

    
Thanks Joe for the reply!

    it’s my first attempt at these numbers and I agree that consistency of POI is what really counts.  Having a tank is what made it possible– pumping’ just too hard to allow me to burn 50 or 60 shots just record chrony figures!

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    JoeWayneRhea
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    I hand pumped a PCP one time , ONCE !! And after I watched a guy fill his Marauder in like 10 seconds with a tank I gave the pump away :)

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    mcdonama
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    “John_in_Ma”How much ai does the tube hold, 190cc, 200cc, 150cc? My S500 has a 231cc tube and will give me 170 shots on reg from 3000-1500psi with a bit tighter spread and deviation. If course i did extensive hammer lightening, played with a half dozen hammer springs as well as different size shims for the valve spring. Oh and the huma reg is set for 110bar.

    
John,

    i think the tube is 122cc.  It’s pretty small– one reason I chose the external Huma design.

    Yes, Huma said the reg came set at 110.  Mine seems to come off reg a bit lower but of course it could be the accuracy of the tiny gage is out a bit.

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    John_in_Ma
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    I would say your gun is doing just fine with shot count and speed.

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    mcdonama
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    Update:
    Approx 500 rounds since the tune so I think things have settled in and stabilized, so I ran another test string and here’s the results:

    filled to 190 bar
    61 shots before off reg
    avg 710.5 fps
    es 10 fps (high 715; low 705)
    sd 2.12 fps

    I’m pretty impressed with this rifle now.  I’ve owned it for several years but only focused on improving it since I had a better air source than a HIll pump (bought a Great White from Joe B).

    I shoot at 30 yards since that’s the longest my backyard allows.  My favorite target is a biathlon style resettable with 5 targets measuring 1.25 inches.  I recently got 3 additional face plates with openings 1″, .75″ and .5″.  Before the addition of the regulator and the tuning, I never tried any smaller than the .75 and struggled to hit 5 in a row.  After the reg and tuning, the .75 immediately posed no challenge– I could go 10 for 10 regularly– so I went to the .5 which is more challenging.  So I figure the rifle was the limiting factor before the tune and now the shooter is limiting factor and I’m on the right track to improving my skills and accuracy.

    Anyway, at .5″, 30 yards is somewhere in the neighborhood of 1 moa, I’m pleased with the results.  Since the AA200 is highly adjustable I think I might experiment with higher power levels.  What effect will increasing the fps have on the consistency and accuracy?

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