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Transvaal,
I fully agree with you on all points you made, except for two:--no offense.
You: "On high quality hand fitted and proper made double rifles the "little" barrel extension seems to work quite as well as the Greener style cross bolt, because it is one of the combined pair of mechanisms that cause the barrels to be locked to the face of the standing breech; and secondly to pull the lumps of the double rifle away from the hinge pin during firing. It is a system that is not generally known how it works to the casual observer, and it takes great skill and experience in fitting during the building of the rifle by the likes of Purdey, Hollands, and Boss." I don't agree with you on this, on your argument for it. It does not lock the barrels to the face of the standing breech, it only holds the barrels down, and against the standing breech; nothing more. If the standing breech has a tendency to flex upon firing, it does nothing to keep that breech from that flexing; possibly cracking, while a doll's head with bite, the Greener crossbolt, the rising bite, and similar bolting systems do help prevent such flexing.

You: " There is also two schools of thought of how the the draw and circle should be formed on double rifles; with one school favoring the traditional circle shape or form and the other favoring the form to be in a straight line angle where more surface area can be had for final locking of the circle and draw together. I favor the straight the angle and this is how I am going to finish the action of a double rifle that I am now in the midst of." I don't agree with you either, on your choice of favoring "straight angle" bearing surface, for clearly, the radial bearing surface (circle) is superior in all respects. An extremely skilled and highly trained Italian gunmaker, trained in European gun making schools, spoke with me about what you are describing. He wrote the following to me; being much better expressed than I could express, so let me share it with you and other readers, in his own words:

In my opinion, the true circle bearing surface is far superior to the flat surface, for two distinct reasons.

The first one is very easy to understand and visualize: Because of the very nature of the design using the flat surface, the two mating surfaces cannot come in contact with each other until the breech is fully closed. The slightest amount of dirt on the breech-face or the water-table, or an oversized shell, even if by only a couple of thousands of an inch will prevent the two surfaces from mating. This of course will put the entire load on the hinge pin.

The same situation would have no such effect with the radial bearing surface (the circle), since the two surfaces are fully mated during the entire opening range.

The second reason is a bit more complicated and difficult to explain without detailed drawings showing the vector lines of the forces in effect. But, I’ll try:

At the time of firing, the fore and aft force acting against the barrel and the breech-face, is not entirely horizontal. On both systems, there is an upward force trying to swing open the breech. This upward force is due to the fact that the hinge pin is below the centerline of the barrels; the lower the hinge pin, the higher the upward force. This force can be easily calculated with the use of a vector drawing.

On the flat surface system, we have an additional force trying to open the action: the necessarily angled surfaces act as an inclined plane, just like a set of adjustable parallels; as they are squeezed together, they try to slide (this is easier for machinists to visualize, as they work with adjustable parallels all the time). This again can be demonstrated and calculated with the use of vectors.

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