The 75 was shooting all over the place because the gun was grocely underweight and the trigger was hard.
It was easy to put some led at the tip and inside the handle.


But the mechanism had to be entirely scrapped. The old one was making it impossible to shoot straight. Here is the old one :

Notice how the arm is short and the notch low and large.
I could not do much about the lengt of the arm since the pin holes were already there. I was able to add only 5 mm of arm but I sure could make the trigger piece a hole lot more sensitive by increasing leverage. I increased the leverage by placing the notch very close to the pin. I had to resize the notch in accordance to it's new position. Making it very small :

The arm sets perfectly into the notch (do not be fooled by the shade).

The mechanism works very well. The trigger runs about 8 mm before the gun fires. Even while using a stiff band i could not feel any resistance on the trigger since the leverage is so great.

I was a bit worried after my initial trials but now that it's balanced and the trigger is smooth the gun shoots very well.
www.renepotvin.com