Gun fastening, the more meaningless the test becomes. A huge part of the ultimate shear limit of an assembly is the actual details of the fastening parameters, such as tube/body clearance, thread condition (fit/finish) screw quality, preload torque from factory, hole clearance/alignment etc.
I suspect any test not using an actual production line gun is going to give only rough approximations, and a test such as use of a bolt cutting tool to measure shear forces only tests bolt cutting tools and the screws used in the test.
One may just as well simply look up the shear limits of 10-32 screws, since its easily found online. That said, the range varies around 100%, based on screw alloy, type etc.