Hi guys! I thought I'd drop in and share some experience and results with 2400 and 158gr bullets.
Firstly, most of my .357 mag loading was several years ago, when I was less cautious and less experienced. But I have loaded an SNS Casting 158gr coated LSWC with 2400. I got as high as 15.5gr with 2400. That was scary. But I've shot many loads with 14.5gr and had no issues whatsoever. QL goes a little wonky when I put that data in, and tells me it's a compressed load at 105.6% and 47,855psi. I can hear the powder moving when I shake a cartridge. QL does not seem to like 2400. It tells me the same kind of story with a 158gr XTP....but we'll get to that.
Accuracy of the LSWC and 14.5gr of 2400 is pretty reasonable as I recall. I've shot many of them through my various GPs, and an SP101. Zero problems. But my notes do not indicate that I completed an accuracy evaluation from a bag, and I have never run them over a chronograph. Not surprising as this was the first load I ever worked up. I plan to chrono some this week, and I really should check accuracy too, but I just might not get to that.
Now for the 158gr XTP. Lyman 50th claims 14.9gr is max even though Hornady is lower. I ran 14.5gr and 15.0gr over the chronograph, and did an accuracy evaluation for both. However, my notes on this load aren't great either. All they say is that the 14.5gr group had slightly better accuracy overall with 10 shots at 1.75" - 2" shooting off a bag at 25 yards (because apparently I didn't care enough to measure it exactly). But the higher load of 15.0gr had a very tight cluster of 6 out of 10 shots. The other 4 made it the larger group, but that could have been my-flinching-fault. The chrono results went the other way, so I cut it back to the 14.9gr in the book and called it good. Figuring 0.1gr couldn't make much of a difference but why tempt fate.
All testing for this load was done with a 4.2" GP100.
14.5gr:
Average - 1245
E.S. - 76
S.D. - 27
15.0gr:
Average - 1252
E.S. - 45
S.D. - 20
I'll chrono the LSWC/2400 load when I can, and a load using the same bullet but 6.5-6.7gr of Unique.
Edit for Update:
In an effort to consolidate the data, here are the chrono results for the two loads using the SNS coated 158gr LSWC.
42-46 degrees, very windy, partly sunny but I found shade for the unit. 4.2" GP100 used at a distance of 10-12'.
The Unique load of 6.5-6.7gr (probably actually 6.5-6.8gr) gave a wide range, but it just a range load.
High - 1097
Low - 980
Average - 1042
E.S. - 117
S.D. - 49
The 2400 load of 14.5gr (+/- less than 0.1gr) gave more uniform results, but nothing too exciting.
High - 1297
Low - 1233
Average - 1261
E.S. - 64
S.D. - 17
Extraction wasn't sticky. The primers looked just fine.
It was too windy to do an accuracy test out there. I was getting jostled around, and I ended up running after the paper plate I had taped up as a target because it came loose and started blowing away. But with this 2400 load, I was able to hit partial (as in already broken) clays at 25-30 yards about 1/3rd of the time from an improvised rest once I dialed in POI a little. I believe it's more accurate than I am in a 20 mph crosswind.
With this bullet, 14.5gr of 2400 doesn't seem like an excessive or over pressured load to me. Just my two cents based on what I've experienced.
