I also do not know of a standard for making this test. Much depends on the equipment that you have available.
As a background, consider the following: there are about 15 0.033" spheres in a half-inch row. In a square half by half an inch there will therefore be about 15 x 15 spheres as a monolayer. Hence there would be some 225 spheres in the sample area. A layer of real S330 particles would contain rather more particles - say 250. Each S330 particle weighs about 4mg so that the mass of 250 particles is about 1g.
Against that background my own method is to glue a 5 mm length of 1" by 1" square steel tube onto a glass microscope slide. 4g of S330 shot (weighed using scales accurate to 0.1g) is poured into the one square inch 'corral' which is then placed on a 'light box' (to give a transmitted light image). The shot sample is then photographed using a digital camera and the image is then transferred to a computer screen. A computer-drawn square of half the edge of the steel tube section is then superimposed on the center of the digital camera's image to become the sample's test area. The number of deformed shot particles is then counted within this half inch by half inch area. Note that the actual mass of shot used has to be adjusted (up or down) to ensure that a monolayer is present in the 'corral'.
The technique described can easily be modified to suit available facilities. The 'corral' does not even need to be square - it only needs to be large enough to contain a sample area of half inch by half inch. Hence, for example, a section of 25mm diameter round tube could be used.
