Trigger Adjustment for Air Rifle

[Gunner_dh]

Hi All,

For a long time I had been wondering why the cheap made Indian AR's do not have any mechanism for trigger adjustment although there is a precedence of the same.
The Pre WW1 era guns had a mechanism of adjusting the trigger with a nut screw via trigger guard.

Is there any cheaper / easier alternative for the same other than working on a lathe machine.

Trigger Adjustment.jpg

Regards
dh