Shooting at 20lbs of clay with the Sam Yang Dragon Claw chambered in .50, with various types of ammo up to 250gr. This rifles uses 3k PSI HPA and fires in excess of 650 feet per second, resulting in muzzle energy of up to 250 foot-pounds.The clay doesn't stand a chance against this gun, and to get complete data I would most likely need to at least double the amount used.
The clay is a generic air-dry sculpting type, kept just moist enough to keep from hardening. I was inspired to film this after Jeff at Taofledermaus used clay to test the damage that some air guns would do (http://www.youtube.com/watch?v=6sj3TTS0__o).
This clay isn't consistent enough for scientific
purposes, but it still gives a fair idea of what pellet is good to use to achieve a certain effect. Plus, it's pretty darn neat, and infinitely easier to work with than Ballistics gelatin.