Hi,

Grip screw lengths:

These vary by grip style. I frames are 3x48 NF and have at least 4 different lengths.

There's likely 3 lengths for K frames;

Rd top (Service) grips
magnas, pre and post war
post war targets

K and N frame grips use a 5x44 NF but here's the rest of the story:

The screw "specification" change of March 4, 1942 was just that: a specification change in the standardization of tolerances for screw thread diameter. A change from old S&W 'smaller minimum diameter' tolerance of .121” - .122”x44 to the larger minimum standardized tolerance of the #5x44 National Fine (N.F.) screw diameter. A #5 screw is nominally 1/8", which is .125”. No, the threads per inch did not change.

It refers specifically to the sideplate screws in this discussion (but excluding the bug screw or upper sideplate screw which is a 4-48 pre and post war) but also to the #5x44 N.F. grip screws. Therefore, there CAN BE a difference between 'pre-change' and 'post-change' screws and they CAN measure differently.

It all depends on how the tolerances "stack up". I have tested this.

Post-change screws may work in pre-change guns, some may be overly tight or some may not work at all. Also worn threads in old guns may give the impression that post-change screws do "work just fine". But very often what we find is buggered and/or twisted off screws.

More typically pre-change screws will work (and sometimes very loosely) in post-change guns because the pre-change screw tolerances allowed for smaller diameter screws to be within acceptable tolerance. Stripped screw holes in post-change guns can be the result of this and are perfect examples.

So although one may "get lucky" on occasion, I always recommend pre war (pre-change) screws in pre war guns and post war (post-change) screws in post war guns.

__________________
Jim
S&WCA #819