313980 is the S&W Target hammer, but they're out of stock.
313990 is known as the Combat hammer and is the hammer that was standard on all S&W Model 66 revolvers including the 2 1/2" version. It's .375 wide.
It's wider than the Service type hammer (.265), but not as wide or as long as the full Target hammer (.500) wide.
The only Model 66's that got the wider, longer Target hammer were some of the 6" barrel models.
The full Target hammer is sort of out of place on a 2 1/2" gun because it's too big for a CCW type revolver. The .375 Combat hammer is perfect.
Last edited by Dfariswheel; January 29, 2013 at 08:33 PM.