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Thread: BAM “Consistency through tuning”

  1. #1
    MOT: Thomson Pneumatic Rifles

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    Default BAM “Consistency through tuning”

    The BAM rifles are set at super-mag velocity levels out the box as has been demonstrated by quite a few new BAM owners and usually shoots from +-1060 to 920 over 40 shots in a straight line progression.

    With just a few basic adjustments to hammer travel and transfer port size better consistency can be reached, this does not require accessing the pressure area of the rifle and so can be performed by anyone handy with a allen key or two. A few folks have already posted shot strings on the forum using such methods and have got quite good results.

    I have just finished tuning 4 BAMs in .177, one in .20 with one more almost complete, but this thread is going to follow the tunes of three rifles sent to me by Taz. They are not for hi velocity tunes but are more for consistency as the threads heading says, so I am also happier with posting velocities on these tunes.

    Rifle one requires velocity ranges between 925 and 960 with light pellets (AA, Acupell etc) and 805 to 830 with heavier pellets (Crosman premier mags, H&N Baracuda etc). I started from the inside out with this rifle re-cutting the FV port to speed air flow and replaced the FV seal with a custom turned “Lifetime” one (the existing FV seal is a one piece nylon casting and will break within 5000 to 8000 shots and there are no spares in SA). Then installed a port interrupter screw to fine tune velocities. First up was the set up for heavy pellets, the results turned out like this:
    1 809
    2 813
    3 814
    4 821
    5 814
    6 819
    7 821
    8 819
    9 823
    10 816
    11 814
    12 819
    13 821
    14 829
    15 814
    16 809
    17 823
    18 809
    19 821
    20 823
    21 813
    22 823
    23 821
    24 811
    25 827
    26 814
    27 823
    28 821
    29 825
    30 829
    31 816
    32 821
    33 819
    34 827
    35 814
    36 816
    37 825
    38 823
    39 823
    40 823
    41 816
    42 811
    43 799
    44 809
    45 814
    46 801
    47 799
    48 803
    49 807
    50 816
    51 809
    52 807
    53 803
    54 778
    55 805
    56 801
    57 793
    58 805
    59 795
    60 789

    Target velocity range achieved, pellets unsorted from the tin and some of the realy odd shots are probably pellets variance.
    Av 813
    Hi 831
    Lo 778
    ES 53
    Sd Av 6 (lo 4fps Hi 9fps)

    Taking 813fps as av and 831fps as Hi and 805 as your low and puting the figures in Chairgun that gives only 7.62mm spread at 60m, more than enough if you do your part.

    That was from a 195bar charge and 140 bar remained so +-0.91bar per shot. A std BAM gives the previously mentioned 40 shot string from 195bar to 110bar i.e. 2.13Bar. Air consumption is better and you now have a power curve.
    I will post the results on the light pellets as well as the different setups with the interrupter screw adjustments. As well as accuracy tests where possible.
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  2. #2
    Inactive Member

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    Hi warrick, got the small ports for FT yet? Still dying for one.....
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  3. #3
    Inactive Member

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    do u guys believe after adjusted stricker screw, the BAM can provide over 90shots consistently @ 16fpe with 1 fill?
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  4. #4
    MOT: Thomson Pneumatic Rifles

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    As much as I believe your Gamo Thread, Ha ha.

    As I said above quite a bit can be achieved by adjustments available on the rifle, above rifle still early days!

    Stopper Ports cut, will email you banking details and price.
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  5. #5
    Sharp Shooter
    Doctor BAM

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    Great tune there, Warrick
    Keep up the good work for BAM.....!!!
    My only question is, what about the accuracy of the Chrony, which was never mentioned....!!! Maybe we need to calibrate a few Chrony's with the results you are getting with the BAM's nowadays.......!!!!!
    The stated accuracy of ~5% on velocity for Chrony readings will throw all your values within single digit accuracies, by the way my maths work....
    By the way, I support Boondock's theory of adjusting the hammer striker screw 100%, but his value of 90 shots was a bit conservative...., it was actually closer to 130 shots.....!!!!! We were probably lucky in that the hammer spring and inside transfer port spring (keeping the port closed), were well-balanced to begin with....
    Happy shooting...

    Malan :jump3 :jump3 :jump3 :love
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  6. #6
    MOT: Thomson Pneumatic Rifles

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    My oversite,
    I use two crono's and Shooting Crony Beta Model and A dedicated air rifle crono, model PM110 from Target Tronics and on back to back tests the difference between Hi's Lo's and Av shots was 1.4% to 1.8%, which variance could just as easily be pellets variance or slight diff in the FV seat. But I think thats quite close enough.
    Happy shooting!
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  7. #7
    Protea FT Team '07/'08/'09/'10/'11/'12/'13
    National FT Champ '09/'13

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    Warrick, you Genius! You have the answer for the AA owners for next years Worlds in the USA, if they're rifles cant be uptuned to 20ft/lbs.(sorry Deon, Jason etc) :rocker

    No, serious now. Your Bam realy impressed me when I shot with it in Durbs. Nothing wrong with the accuracy, and the trigger was impressive. With consistancy like that above, and the good barrels we know the Bams have, I think you have a good value for money winner there. :thumbsup
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  8. #8
    MOT: Thomson Pneumatic Rifles

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    I have always said its the jerk behind the trigger and not the rifle that makes the shooter (yes before I get the Ja but's, a good rifle in the hands of someone who can shoot does make a difference), I was very glad when you had a go with the Bam Piet as it just proved the above, 6 plates 6 drops and all you did was estimate the range as we had shot it that day and dial in.
    That same rifle was shooting to a quater inch accuracy at 50m when I was zeroing off the bench. And if you look in my gallery you will see the groups my previouse FT tuned Bam returned.
    This thread was not posted to say "Gee look at me I am a Great Airsmith", (or Genius, thanks for the though Piet) it was posted for general info and to point out that the Bam's are very versatile rifles at a reasonable price!
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  9. #9
    MOT: Thomson Pneumatic Rifles

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    After Thought on Piets comment, the above rifle is running very throttled and it will still produce 60 to 70 shots at 18fpe, which I have seen on most of the US postings is about what the majority shoot for US FT.
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