Pedigree update...

Guess what?  It turns out my vet was right, Pistol is part foundation quarter horse!  I heard back from the barn owner, and she had found his sire and dam for me, and found out that apparently he is registered with the ApHC.  His sire is Clarktowns Mr Doc, and he is a GORGEOUS foundation quarter horse.  His dam is 50 roses, and I have not been able to find a picture or any record of her, but according to the barn owner, she was a really pretty appaloosa.  So... that explains why Pistol looks like a foundation quarter horse, and it explains why he is still growing.  His sire is 16 hands, and Pistol is a little over 15 right now, but still filling out.