Don, most of the targets thrown today, at clubs I have been to, are BIOs, biodegradable targets made primarily of limestone and sulfur. When they first came out many thought they were harder to break than the old "clays" made with a high amount of pitch. Pitch is toxic to hogs (as if that mattered a whole lot) and do not biodegrade, at least not in a looooong time. I believe the BIOs may be a bit harder to break than the older targets, too.
I know of no data on what is required to break one. How could you possibly determine that anyway? Because rotational forces play such a great part in the breaking, when hit marginally, one would have to take into consideration all the differing rotational speeds that are encountered on different presentations, how early or late in the flight of the bird it is shot (rotation slows as the bird travels), the type target (battue, rabbit, standard, midi, mini, etc.), moisture content of the targets ............ ad infinitum.
Center the bird with your hot core. Make that your goal every shot. Tighten up the choke to achieve higher density in the pattern, don't screw in the most open choke you think will break a particular presentation as you are setting yourself up for chips and lost targets that are hit by one to three pellets that do not break. JMHO, of course.
SRH
