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Thread: Slight Mod improves BAM B51

  1. #1
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    Default Slight Mod improves BAM B51

    When I got my B51, I could not fill it above 150 bar, and it used more air from the cylinder than I do during a deep dive. Since then, I've changed the "Striker Main Spring" as well as the "Port Bush" having the i/d drilled smaller than standard, and these are the results, Filling to 195 bar before each String of 25 shots each. I used a F1 Chrony to get these results.

    Baracuda--- Finale--- JSB
    Match----- Match----- Predators
    1- 915.1----- 1- 970.7----- 1- 964.9
    2- 909.4----- 2- 969.9----- 2- 961.0
    3- 907.1----- 3- 967.5----- 3- 957.0
    4- 906.7----- 4- 971.5----- 4- 951.0
    5- 901.1----- 5- 965.6----- 5- 951.1
    6- 899.7----- 6- 960.2----- 6- 949.2
    7- 897.2----- 7- 956.8----- 7- 945.0
    8- 893.5----- 8- 949.4----- 8- 936.9
    9- 897.3----- 9- 948.0----- 9- 938.3
    10- 885.9--- 10- 947.1--- 10- 940.7
    11- 878.6--- 11- 943.4--- 11- 937.9
    12- 878.5--- 12- 942.0--- 12- 934.6
    13- 878.3--- 13- 930.8--- 13- 926.0
    14- 880.5--- 14- 933.5--- 14- 923.1
    15- 872.2--- 15- 929.6--- 15- 917.3
    16- 873.1--- 16- 928.2--- 16- 915.1
    17- 864.3--- 17- 922.5--- 17- 909.1
    18- 866.6--- 18- 924.8--- 18- 906.1
    19- 856.6--- 19- 918.6--- 19- 903.1
    20- 856.8--- 20- 911.5--- 20- 904.2
    21- 854.7--- 21- 912.8--- 21- 900.7
    22- 852.8--- 22- 908.2--- 22- 898.5
    23- 851.6--- 23- 907.8--- 23- 896.5
    24- 848.6--- 24 - 904.0--- 24- 894.9
    25- 845.9--- 25- 903.2--- 25- 879.7

    After each String, I refilled, and the the valve re-opend at the following pressures.

    165 bar 160 bar 165 bar

    I would appreciate the opinion of the members, to air their views on these velocities, and the capability of hunting Rabbits, Crows Guinea Fowl etc.


  2. #2
    Marksman
    The Guru

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    Unfortunately your velocity spread is far too high, especially if you want to use your rifle out to 50yds.
    The point of impact will vary quite drammatically between the first and 25th shot.
    I have tuned quite a few BAMS and in my experience what really helps is a reduced transfer port and some lightening of the striker spring preload.
    The best I got out of the BAM was when I got it to shoot at 12ft\lbs with a velocity spread of about 25fps over 80 shots...pretty much the same as an S400

  3. #3
    Inactive Member

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    Brandon, what did your shot spread look like when filled to 150 bar with the original spring? In an ideal power curve the velocity should increase first after every shot before dropping off. The spread you have posted looks like only half a power curve, with the velocity dropping off after every shot from the beginning.

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