I was just mentioning how the strength numbers apply to an adhesive.
If the trunnions are installed in a hole machined in the sides of the barrel and held in place by some glue, the metal holes and outside diameters of the metal trunnions take most of the load if the barrel is fired.
If the trunnions are just glued to the outside of the barrel, the glue will be taking the shear load when the barrel is fired.
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As for static pressure, that only exists before the powder lights. When the powder explodes, things are anything but static.
When firing a 1 ounce powder charge with nothing else in the bore, the gun is basically firing that powder out of the muzzle. That is a 437.5 grain projectile equivalent.
What most people forget is the weight of the powder is being expelled from the barrel and this powder weight creates recoil.
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In this case, it is 7000 grains/pound divided by 16 to find out what the powder weight is. In other words, one ounce of powder weighs 437.5 grains.
A 437.g grain projectile equivalent would compare with a firing a 278 grain .570 caliber lead roundball from a gun using 159 grains of powder. (278 + 159 = 437)
The recoil will probably be different based on the weight of the cannon barrel but a one ounce powder charge will create enough recoil that it should be considered before touching it off.