4" J frames
I have a few 4" J frame Smiths, Also recommend not altering your gun but purchasing another for many reasons....
I recommend the 3" bull barrel RB 36-1 or SB 37 airweight in 3" because they seem perfect for me.
The J frame model 30 in 4" seems 1" too long for some reason.
The square butt model 34 with 4" barrel in 22 is a perfect trainer for those that find the k frame model 17 or 18 too big.
Pictured below is a 4" barrel model 34 Square Butt in .22 L.R. with adjustable sites
Here is a RB model 30 in 32 long with 4" barrel above a model 37 Airweight with 3" barrel (Below)
Shown together top to bottom all J frames,
Model 34 with 4" barrel and SB
Model 37 with 3" barrel and SB
Model 36-1 with 3" bull barrel RB (as issued to NYPD female officers)
Model 36 with 1 7/8" barrel RB