That is my only explanation for it, too, Don. The owner of the choke tube business' standard reply is, "The stuff (HeviShot) is harder than what the barrel and the choke tubes are made of .......... when it bridges as it enters the constriction, what do you think is going to give?". I agree with him, but also that the odd shapes and sizes contribute to the bridging.

SRH

May God bless America and those who defend her.