HT-FRT adapted for milspec lowers. Every part has been updated.
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
Use a spare Bolt Catch Spring.
This requires a milspec lower, a "milspec" semi-auto FCG, and a 'standard' full-auto BCG. The 'plate' file will replace the disconnector and disco spring.
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 plate_adjust.png, file or sand a little bit off in the red area, test fit, and repeat until the BCG doesn't drag.