Hey Sean,
If you want to know more about recall pens try WWW.gamebird.com or Lion Country Supply at www.lcsupply.com, I think they both sell plan for building them. I have seen them, they do work well. As for introducing your dog to gun fire, I'd go with what the others above stated. A staters pistol at feeding time, at out door play time and work your way up to training loads. Kent Shot shell makes a nice 12 ga taining blank. If you reload you can make you own. What breed of pup did you get? Hey thanks for the chukur info.

John