Interesting. I thought that the 27 series pretty much ended with the 3's but, obviously not. I have a 3. It's not pinned or recessed. Have you checked the Smith & Wesson Standard Catalog to see what engineering changes were involved with the 5? Such as, for example, the substitution of MIM parts for previously used forged parts? Would that be one of the changes? I'd love to see a photo and find out how it shoots. What did you pay for yours?