The crimp tightness can make a difference in the accuracy. I have not been working with accuaracy too much with my 38 and 357 loads, but one guy I shoot with will find a load that seems to work and then start working on the crimp. I had a 375 H&H loads that worked fairly well, but once I used a Le factory crimp die on it, the groups dropped in size by a good 33%.
If you are loading for the lever also, make sure the crimp is fairly tight; if it is not (especially with a 357 laod), it may start pushing the bullet back into the case which can spike your pressures. Also, if the crimp is not tight enough, the case motuh may catch and cause feeding issues (learned from personal experience). One way I test the crimp for my lever loads is with a kintetic bullets puller (hammer type). I will place the crimp I want, and then pull the bullet; if it comes out easy, I crimp it tighter until it takes some force to dislodge it.