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Oh, no! My FreeFlightHammer won't cock! What now?

May 29 2017 at 4:10 PM

Steve in NC  (Login pneuguy)
Crosman Forum Member
from IP address

Any successful PCP tune depends on arriving at correct settings for a number of variables, one of which is hammer valve-strike energy. Adjustment of hammer energy is easy with an FFH, provided that adequate energy is available before the setting is max'd out.

Maximum FFH strike energy is achieved by setting free-flight distance to just slightly greater than zero, provided that doing so doesn't interfere with cocking, which it sometimes does. For example, when an FFH is used with aftermarket hammer springs wound with more coils or thicker wire than stock, the spring may compress to coil-bind and prevent cocking. This post is about what to do when this happens.

Fixing an FFH failure to cock consists of first measuring the amount of hammerspring interference that's preventing cocking, then...

1. readjusting (increasing) FFH length in the Mrod and Prod FFHs, or...
2 removing preload spacers in the QB78/CR160 FFH... the amount necessary to restore proper operation.

Here's how.

Verify that gun is uncocked and unloaded.

1. Reduce FFH free flight distance by turning the FFH adjustment screw clockwise (in) until an increase in resistance is felt, indicating a free flight of zero. Then back the adjustment off (turn counterclockwise) by 1/2 turn.

2. Attempt to cock. If successful, go to step 4.

3. Otherwise, back the adjustment off by 1/4 turn, keeping track of the total number of whole and fractional turns, and return to step 2.

4. If no counterclockwise adjustment was needed to allow cocking, you're done. Otherwise...

5. Calculate the preload change required from the number of turns (and fractions) measured in step 3 according to...
i. Number of turns x 0.05" for the Mrod FFH...
ii. Number of turns x 0.042" for the Prod FFH...
iii. Number of turns x 0.025" for the QB78/CR160 FFH

6. Increase the length of the FFH assembly by calculated number in step 5 for the Prod and Mrod FFH, remove 0.125" spacers equal or greater to the number for the QB78/CR160 FFH.

Additional documentation can be found here...


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(Login Mike17670)
Crosman Forum Member

Good to know!

June 1 2017, 12:29 PM 

Thanks again Steve.

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