Buildus Interruptus

[PVBoom]

It's unclear to me what your problem with the bolt release is. More details please.

Mil spec lowers have external lugs to take the retention pin of the bolt release/catch. Mine doesn't.
Look at the picture of my lower, increase magnification as needed. The vertical slot above the mag release/catch is where it mounts.
The retention pin holes are internal to the lower, not external as per mil spec.