river j
Reading your post it sounds to me like your trying to patch a small jacketed bullet for the larger diameter .38. I never have heard good results patching a jacketed bullet, and I never tried it my self, so I cant say.
If you get the patch to thick and you use smokeless powder,you are flirting with high pressures.
A .38-55 takes a .3775 diameter bullet, or a 9.58 mm.
I would go with a proper cast bullet if you don't want to shoot the high priced Jacketed bullet and be safe.
I think you would be better off using a .375 (9.53 mm) grooved cast bullet and using a PP jacket patched 1 or .002 over bore diameter, and work up a safe load.