Still puzzled, I lucked onto taking off one of the caps and peering down inside the blind mortise
The Mark-VII has a fixed magazine in a blind mortise
in the stock that is easy to fill and feeds flawlessly.
The blind mortise
and tenon joint is fully customizable for size and position of the tenon and mortise.
Yang and Lin (1986a, b) investigated the effect of tenon fit and the effect of joint geometry factors on the strength of blind mortise
and tenon joints and found that maximum bending moment capacities were obtained with tenon/mortise fits of -0.
Cal Door uses blind mortise
and tenon mitered joints for all of its five-piece mitered doors and glue and press fit applied mouldings.