The major stress on a double gun is "Axial". On many designs nothing contains this but the hinge pin. Some models have auxilarry fastenings for this purpose, ie cross bolt, rotary bolt, doll's head, forward face of rear lug on a dbl underlug etc,etc. All these require proper & precise fitting to be of benefit. Many think of the most requirement being a rotational bolt. Both W W Greener & Dan Lefever stated many years ago a gun could be kept from opening by merely wrapping ones thumb over the bbl. Those "Two Litle Pins" are entirely adequate to hold the bbls closed & if you note, at least on most Berettas, the lug the pins enter are recessed into the frame wall thus supplementing the hinge joints against the axial thrust, a feature lacking on many O/Us.
