I would agree with the opinion that .358" is the proper size-to diameter.
If you decide to go "all out", every now and then a Hensley and Gibbs #51 shows up on ebay. That is the Cadillac, to me...
+1 on the .358 sizer
H&G are excellent molds & the #51 swc is an excellent bullet. If you look around there's allot of "custom" h&g molds out there. One of my favorite h&g molds.
51358 ='s 1 cavity is the #51 swc bullet design & casts a .358dia bullet that weighs 160gr.
50358 ='s 1 cavity is the #50 wc bullet design & casts a .358dia bullet that weighs 148gr.
One mold with 2 different classic h&g bullets, their famous #51 swc & #50 wc. I store my molds with grease in them to protect them.
Take your time & look around there are many different bullet molds out there for the 38spl's. I own several:
raphine 150gr hb fp
lyman 35870 147gr hb fp
lyman 358395 148gr hb wc
lyman 358477 140gr hp swc
lyman 358156 150gr hp swc
lyman 358439 158gr hp swc
lyman 358093 125gr sp
h&g #51/#50 160gr swc/148gr wc
h&g #51/#51hp 160gr swc/150gr hp swc
h&g #50bb 10-cavity 148gr wc
Mihec hbwc 4-cavity 148gr hbwc
Mihec 359-640 4-cavity 158gr hp rnfp/ 170gr solid points
cramer 2-cavity 158gr hp rn (known as the hunter special)
cramer 2-cavity 110gr wc
hb ='s hollow base
hp ='s hollow point
bb ='s bevel base
sp ='s spire point
You can never have too many excellent molds for the 38spl/357.