The watered down version:
You want the bullets sized to the holes in the cylinders or a hair smaller. You want to load the bullets so they are out into the leade's of the cylinders.
A picture of 38spl reloads I took back in 2014. The bullet on the left is a mihec 640 series 158gr hp that has an upper and lower crimp groove. The 640 bullet is crimped long/in the lower lube groove in the 38spl cases & is sized to .358". The wc on the right is the H&G #50 148gr bbwc sized to .357" and crimped in the middle lube groove.
test targets/6-shot groups @ 50ft that are nothing more than the targets I used that day to test those 38spl reloads pictured above in a s&w 686/357mag.
Playing around @ the 50yd line testing plinking/blammo ammo using 357mag brass and a 158gr hp (cramer hunter rfn) and that 640 bullet. The cramer was seated in it's standard crimp groove, the 640 was crimped in the top crimp groove, both sized to .358"
Ugly target shot for my own testing all 4 groups were under 2 1/4" outside to outside measurements.
I've showed this target before and it's like you could here a pin drop. In reality those loads are nothing more then borderline acceptable for 50yd accuracy standards. Hence the term blammo/plinking ammo. It's cheap to make, free lead for bullets, a primer & 5.5gr or 6.0gr of powder. Need to retest @ 100yds to decide on 5.5gr vs 6.0gr.
A couple of links to what Ed Harris wrote about the making of the 38spl wc/hbwc reloads and what kind of accuracy Harris considered acceptable @ 50yds with those wc/hbwc reloads.
http://www.hensleygibbs.com/edharris/articles/38wadcutterQA.htm
http://www.hensleygibbs.com/edharris/articles/38sagafiftyyards.htm
Seeing how your using a 357 might as well add this link. Most of what Harris wrote in this article I agree with & is a good place to start. But you will find thru testing of different alloys/water dropping your own cast bullets & now the introduction of coated bullets. Your reloads/bullets will be tweaked to your needs/performance/accuracy.
http://www.hensleygibbs.com/edharris/articles/primeronloading38specialfornewbie.htm