Are we sure they can't all be shot unlocked?
I suspect that is quite true. It is rather hilarious to read all the advertizing hype on triple, quadruple etc bolting to hold the gun closed, the forces tending to "Open" the gun on firing are rather low. The main purpoe of Greener's cross bolt, which he explained quite well, was not to help hold his guns shut, but to help hold the breech up against the back thrust of the fireing shell without bending back. Many makers did use bolts etc to assist in taking the load off the hinge joint. The Baker Draw bolt was for this purpose as was the forward face of the Purdey rear underbolt. Neither of these however contributed much, if any, resistence to the breech flexing reaward. This requird a fastener at the top which "Held the Breech to the Barrels". A single bolt as on the 21, Parker etc is quite suffecient to hold a gun shut with even the most powerful loads.
McIntosh totally missed the point when he insinuated Alexander Brown didn't know what he was speaking of when he stated the secondary function of his rotary bolt was to hold the breech "Up Against the Barrels". Brown knew exactly what he was talking about, Mac didn't understand, for he said the purpose was to hold the barrels back against the breech. The force from firing has much more push Back against the breech than it does in pushing the barrels forward.
