Recently I picked up a small set of humpback hammers that were being offered as a group. One was a centerfire K-frame hammer, so earlier today I swapped hammers on my M&P (1905 Fourth Change) Target model just to see what the result would look like.
Before:
After:
Oblique close-up, with oily thumbprint (!!!):
I'm not that sure I like either the functionality or the appearance of the overall configuration. I think HB hammers may look better on N-frames than K-frames. And since I have an inflexible tendon in my right thumb (Dupuytren's Contracture, very irritating on that digit), the extra fraction of an inch that I have to stretch up to contact the hammer spur puts it almost out of reach. That defeats the very concept of easy recocking that Douglas Wesson called out when he filed the hammer patent in 1937.
Cocked:
I'm not sure I think the profile of the gun looks any better when it is prepared to fire in single-action mode. I understand that we are talking performance rather than attractiveness here, but the gap between the frame and cocked HB hammer is kind of unattractive compared to the closer approach of the standard hammer.
This was an interesting swap-out for me because the sear that came with the HB hammer proved to need some work. Here's a photo that shows the tip of the sear will not be engaged by the trigger on a double action pull; the bevel on the trigger pushes the sear in and the hammer will not move when the cylinder rotates. I worked on the surface above the pivot point and improved the lower contact picture, but it still needs more work. I'll get it eventually.
I'll acknowledge in closing that this gun could never have shipped with a humpback hammer, because it left the factory in 1935 and the first HB hammers became available in 1937. I also know that the gun shipped without a Wesson grip adapter; the one on the gun now was added at a later date. So in this configuration the gun has two features -- hammer and adapter -- that were legitimate options or accessories for later production of this model but were not on this gun when it shipped.