I started reloading revolvers in '69 and seated all cast bullets to the crimp groove. On every revolver reload since I have seated to the crimp groove or cannalure and disregarded book OAL, and as long as the cartridge was not too long for the cylinder, there were zero problems. I always thought the bullet designers knew where to locate the crimp groove and have loaded many thousands or revolver rounds quite safely (and accurately) seating bullets to the crimp groove. I don't know how the test labs figured the OAL for cast revolver bullets, perhaps the dimensions noted were what they arrived at with the bullet they used crimped correctly, in the groove. But often the crimp groove was hidden in the case or out too far if I used the book OAL...