Mr. Ayoob: First, I've been reading your writing for most of my life and I would like to thank you for letting me benefit from your work and I would also like to thank you for responding to us personally on this forum. I'd like to know what you think the more valid techniques for measuring ballistic effectiveness are. I think opinions vary widely on this. On the one hand, I have the three Marshall and Sanow books and I frequently reference the one shot stopping percentages they list. On the other hand, a trusted shooting instructor is a retired SWAT guy and he prefers to rely more on gelatin tests. I would appreciate any feedback that you might have on this subject.