I haven't shot a ton of 38's but I have in other larger calibers, 357,41,44, 45C, & 454. Before I married the gal I have spent the last 40yrs with, we were shooting 357, 41, and 44mag at the rate of several hundred rounds each a week. That continued for a year or so after we were married. These were top end loads for each caliber.
At the time I was using whatever brass was the cheapest because with the higher pressures it required heavier crimps and that led to fatigue and failures. I have had the occasional split mid case over the years but only rarely. I found quite by accident that when crimping what your mind says is good is usually more than is needed.
When I set up now for a new load, I will load a dozen rounds up, load 6 and fire 5, checking the length on the last one after each shot. If it moves, I adjust the die a bit more, maybe a 16th of a turn, as it doesn't take much in most cases. Once that is done I repeat until no more movement is noted. I know this sounds like a lot of extra effort, but in reality it only takes a few minutes. I have a small press that can be mounted on a bench and use that to get things set. Once set I can easily run a hundred or so rounds through it at the range or back at home.
If you cannot set up at the range then you can put some marks on the top of your crimping die to use for adjustment. Using a sharpie, you can mark it at 12, 3, 6 & 9, call them 1,2,3,4. Then go back and mark it in between for 1.5, 2.5, ect. . Then adjust it down until it is just taking the flare off the top rim of the case. That will be zero and you can mark the body to correspond with one of your other marks. I usually use the mark facing me as #1 and go from there. This way you can adjust the crimp in increments accordingly you can shoot them in order at the range. You will note that one set of rounds will shoot better than, even if only slightly, the others. That is your crimp setting.
Try this at 25yds using a rest and you will find your most accurate setting for that given load. If any bullets in the first set move any at all then stop and move on. I do not shoot competition, but i do hunt with my revolvers and have for the past 40'ish years. I put accuracy first and foremost with all of the loads I shoot and strive to get them there. this little drill has made a big difference in how well things have shot over the years, and it is something simple to do, but takes a little time. I can say that even running my 300gr 454 loads at 1600fps the crimp on the bullets even the cast lead is not really all that much. Just enough to hold the bullet still. The case tension should do most of the work. This is somewhat what I am referring to, the groups were shot offhand at 40yards through my friends revolver, he was having issues with getting the load to group. The group on the left was his initial crimp and the right were backed off about an 8th of a turn,
I could have done better but with the wind and being unfamiliar with his Custom Shop 657 it is what it is.
I use Starline brass almost exclusively, but also have all other brands on hand as well. The brad really doesn't matter, the case tension and crimp do no matter which brand you use. That said, and as has been mentioned if your seeing split necks in your batch of cases, it is time to get new ones. A box of 500 from Starline will last a LONG time. I've been running my 41 cases for going on 8yrs now with probably a dozen or so loads top end loads on them and they still work just as well as they ever did. Same with the others, I generally get loos primer pockets or loose them in the grass or woods while hunting before they give up to splitting.
