Analysis
Primary Requirement:
Reduce Trigger Force by 1-1.5 lbf
The proposed design consists of a standalone module that would interact with existing fire control groups. This unit functions by engaging or disengaging a spring which provides upward force on the back of the trigger bar. This cancels out part of the force of the prep spring resulting in a lighter trigger weight. The manufacturer advertised pull weight of two common trigger groups are shown to the left. The drop in module would have the effect of shifting the graphs down by 1 lbf when engaged.
​
Manufacturer advertised trigger pull values are overlaid with lines representing the calculated break values of stock triggers. The calculated value for a stock milspec trigger was 7.66lb and the Geissele SSA is 4.53lb. The calculated reduction from stock the module provides as a function of degrees of rotation is shown in the excel table. Important points of Break and Over-travel are denoted. At break there should be a 1lb reduction and 1.25lb at over-travel.
Figure 2-1 Calculated Trigger Force Value
Table 2-1 Calculated Force Reduction
Figure 2-3 MilSpec Force Calculation Page 1
Figure 2-4 MilSpec Force Calculation Page 2
Figure 2-5 SSA Force Calculation Page 1
Figure 2-6 SSA Force Calculation Page 2
Force on Trigger
Module Assist Force
Trigger Spring Moment
Figure 2-2 Primary Forces
Stock
Module