Something to keep in mind is the poi compared to the poa.
Most of the s&w snubnosed 38spl revolvers are setup (sights) for 158gr bullets. The lighter bullets will impact low with some of them being extremely low. The other thing to keep in mind is that some powders do better with heavier bullets (158gr and up) in the 38spl's compared to the lighter bullets.
Not all bullets are created equal, the different material they're made out of (lead/jacketed/plated/coated/etc) makes a huge difference. The size/shape/depth of the hp comes into play along with the bullets body & bottom drive band. Most of this doesn't matter with the longer bbl'd firearms but with the short bbl's everything makes a difference.
I you do a little searching on the web you'll find articles on reloading for the snubnosed revolvers. This came from 1 of those articles/searches.
Back in feb-mar of 2012 handloader magazine (#276) did an article on 38spl p+ reloads for the snubnosed revolvers using a snubnosed ruger lcr (1.875" bbl) for a test revolver. In that article Brian Pearce stated the lcr compares to the s&w 637, he was also trying to duplicate the 20A Buffalo bore 158gr lead swc gc hp 1000fps snubnosed revolver load. Pearce ended up duplicating that load using 6.3gr of power pistol and a rimrock 158gr lead swc gc hp. If you look at the table above the 5.6gr load using a zero bullet is about worthless.
A couple of years ago I did a little testing with a charter arms undercover 38spl that was p+ rated (2" bbl). Found out rather quickly that cast & cast/coated bullets had higher velocities then their commercial/store bought jacketed counterparts. I also found out that the lighter faster bullets shot a lot lower @ 7yds compared to the heavier bullets. I was getting 1100fps from a 110gr cast/coated bullet in that 2" bbl'd revolver but it was hitting 7/8" low. Same with mey 125gr cast/coated bullets, 1050fps and 6/7" low. So I started testing these 150gr to 160gr bullets in that snubnosed revolver.
As you can see big differences in the hp's, typically the slower the bullet the larger the hp. The top right bullet and the bottom center bullets are interesting. The bottom center has a small hp hole that is a cramer bullet from the 1940's called the "hunter" bullet that was designed for the 357mag. The top right bullet is a common lyman 358156 (similar to rimrocks & buffalo bores lead swc gc hp), what makes it different is years ago you could special order the hp size for the hp. Standard hp sizes for the lyam hp pins were .125" for the 9mm/38spl/357mags but you could order a custom mold with a .140" pin or a .156" pin (both common in 44/45cal molds). That bullet was cast with a .140" pin.
Out of those 8 bullets pictured above and 2 that weren't in the picture, testing 10 bullets and 5 different powders. 4 bullets kept having the highest velocities. I'm talking as much as 70fps more velocity by simply choosing 1 bullet style/design over another. These are those 4 bullets.
What they have in common is the ability to seal the cylinders and bbl quickly with their large bullet bases or long solid bodies.
Left to right: cramer # 26 158gr swc hp/mihec 148gr hbwc turned backwards/lyman 358156 154gr swc gc hp/home swaged 150gr fn hp
That mihec 148gr hbwc mold can also cast a 170gr wc that is an absolute thumper. I ended up going with this bullet a mihec 640 series rfn bullet design that casts a large hp holed 158gr bullet or a 170gr solid nosed rfn bullet. I'm getting 950fps using 6.2gr of power pistol and either bullet (158gr hp or 170gr solid nose) in that 2" bbl'd snubnosed revolver.
All the bullets I cast are 8/9bhn pictured above, same alloy for the core in that jacketed bullet pictured above made out of a 9mm case.
An excellent tool that a lot of people don't use or talk about is a forester case trimmer. You can buy a hp tool for that case trimmer to put your own hp in any solid nosed bullet or re-design existing hp's. It comes with a 1/16" and 1/8" hp bit. But you can also use a .1875" (3/16") drill bit or 60* center point drill. I used a forester hp tool that I picked up on e-bay (trimmer/collets/pilots/hp toll) for $35 delivered to the door. What a bargain!!! Anyway I make these 210gr hollow point hollow base lead/coated swc's for a 1000fps 44spl snubnosed revolver load.
It all starts with the bullet selection. Pick the wrong bullet and the rest doesn't matter.