And here's MkII and MKIII instructions gleaned from this thread
need info on trigger adjustments for Mark II
BSA Martini MKIII trigger adjustment
The MKIII trigger is the same as the MKII
Adjustment of the trigger Before Leaving the factory the trigger is set to a pull-off weight of just over 3 lb., but provision is made and an Allen key provided to carry out subsequent adjustment. It is not necessary to remove the action.
Two Allen screws are located in the front of the trigger guard and locked in position by two locking screws, one on each side of the guard. To lighten the trigger pull slacken the screw which locks the adjusting screw marked "T" with the Allen key provided. Turn the screw "T" in an anti-clockwise direction until the desired weight is achieved. Re-lock the adjusting screw and re-test the trigger weight. If the trigger weight is to be increased the above procedure should be followed, but the adjusting screw "T" turned in a clockwise direction. A minimum trigger weight of less than 1/2 lb., can be obtained. It should be remembered, however, that where a very light trigger weight is being used the rifle must be handled with care and the cocking lever closed gently.
The unmarked screw in the guard controls the backlash (the amount of trigger movement after the release). To decrease backlash first cock the rifle and then unlock the screw and turn it in a clockwise direction. This should be done 1/8 of a turn at a time, testing after each movement to ensure that the trigger will release. After the adjustment the locking screw must be retightened and the let-off retested.
DO NOT attempt under any circumstances to oilstone the sear engagement faces. Great care has been exercised at the factory to produce correct sear engagement. Hand stoning will upset the precision with which these components have been manufactured. This may produce an inconsistent let-off and, where a light trigger let-off is being used, could cause premature firing.
