doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com How does a greener cross bolt work?

I recall lamp blacking the bolt and the rib extension on my Francotte, and I was surprised and disappointed to see that the back edge of the bolt did not contact the back of its bite. But I suppose that it may still have done so when the gun was fired.

Greener condemned the Square Bolt as having stress points in the corners. His to my knowledge were all round.

Greener also condemned the way his design was executed by many other makers. Like redoak stated above about his Francotte, the fit was not of a standard to be doing any real work.
I have three guns with the Greener cross bolt & one of them is a La Sorda (Spanish) that has had a new hinge pin fitted to tighten him up. Even though it brought the barrels back to face only by a matter of a few thou" nothing about the cross bolt operation or fit changed, it contacts on the bottom 1/8 of the rib extension hole.
The other two are British & one contacts on the bottom 1/4, while the other contacts the bottom to rear 1/2 of the hole.
So I suppose that they are doing something for lockup even though it is now claimed by some manufacturers that they are not needed due to metallurgical improvements & the strength of the Purdy double bite under bolt. As is the claim for all third bites & the reason why some new guns don't have them & rely totally on the under bolt.
I like the Purdy hidden third bite as it seems to add another wedging type latch that wedges over the top, in opposition to the under bolt.
The Greener cross bolt is more security in the psychological than the physical unless meticulously fitted.
O.M

It seems to be, from what I've read anyways. Seems a marketing ploy of the era was to advertise improvements in lock strengths, even when a bit excessive. I suppose we could figure out just how necessary the cross bolt is if we knew the amount of force being applied to the breech face and under lugs on firing, and see how that compares to the mechanical properties of past and present steels.

I do not recall reading in any of Greener's writing that he considered the cross bolt as being needed to assist the underbolts in keeping the barrels closed. He did cite a case in which he constructed one of his guns with the crossbolt being removable by a knob on the end rather teing connected to the op lever. He fitted fixtures on the top rib & the breech so could stretch a thin non-elastic mat'l across the joint. He fired different loads both with & without the cross bolt inserted.
He stated his gun took all normal loads without rupturing the "Gage" even without the cross bolt but as he increased the load it began to break it. He went to still heavier loads with the bolt inserted & never broke it with the bolt being used.
The Doll's Head was of course designed for the same purpose. Many of them do not even have a bolt fitted so obviously do nothing to keep the gun closed. The original Westley Richards as do most Lefever Arms Co guns use only a bolted Doll's Head with no further bolts.
I have an old H grade Lefever "Parts Gun", the only one I have tried this on, but I can take the ball hinge completely put of the gun & reassemble it & it bolts up tight with only the doll's Head securing the breech & barrels together.
When a charge is fired there is definitely "Back Thrust". If there were not then any recoil or blow back autos simply would not work.