Chuck;
For the Doll's Head to be effective it has to be amply constructed & properly fitted. The square shoulders developed by Dan Lefever were in my opinion a great step forward for a doll's head. It then becomes in principal just like a T-Bolt in a milling machine table. It will slide freely down the slot, but when the nut is tightened if enough fore is applied you can pull the bolt in two but the head will still be in the slot. Likewise in closing a gun the doll's head swings freely into its recess, but when the axial thrust thrust is applied it adds support to the top of the standing breech, lessening the springing back of same. This is the same purpose for which W W Greener developed his cross bolt. Also in designing the rotary bolt Alexander Brown envisioned, & so stated in his patent, it being fitted to "Both" hold the bbls down & also to hold the breech "Up To" the bbls. Apparently after Brown left this "Dual Purpose" was not much adhered to, the rear surface not being fitted which reduced its effectiveness to no more than the flat bolt of a Lefever, Baker or 311 Stevens. Only the Lefever though incorporated the doll's Head. The forward face of the rear lug of a double underlug (lump) if properly fitted will take virtually all the strain from the hinge pin in absorbing the axial thrust, but add nothing to the standing breech. Enough off-face guns abound to attest most are not that well fitted. Good design & proper workmanship produced some superb guns long before such alloys as 4140 etc were readily available to the Gunmaker.
It is of course readily admitted that many guns have been built relying solely upon adequate integrity of the frame itself to contain all forces applied upon it & have sucessfully done so.
I did once consider, but never got it done, removing the ball screw from that above mentioned H grade parts gun & strapping it into the Firestone "Bench Rest" & firing off a load via a long cord & see if that doll's head was amply strong to take the whole nine yards of a regular shell.
