For a basic milspec lower with the sear block hump above the standard safety, print these files:
    1_block - wide - remix.stl
    2_plate - remix.stl
    3_safety - mirrored_2x_wide - remix.stl
    4_pin.stl
    
If your lower does not have the sear block hump and you want a bit more engagement, print these instead of their reciprocal above:
    1.1_block_wide - remix.stl
    3.1_safety - wide - remix.stl
    4.1_pin.stl
 
I printed these with eSun PLA Pro, but any quality PLA+/Pro should be fine.  Use a high number of perimeters, and high percentage of infil (grid, lines, rectilinear, or similar).  I used 6 perims and 60% line infil.

If your BCG is stiff to pull back, it is dragging on the hammer because the plate is slightly too tall, and doesn't allow the hammer to retract far enough.  Referencing pics/plate_adjust.png, file or sand a *little* bit off in the red area, test fit, and repeat until the BCG doesn't drag.
