Some time back I noticed that the 357 SIG case has more capacity than the 38 Super. Then I seen that Alliant list a load using 2400 in 38 Super using a 147 gr. bullet. So the curious squirrel cage started whirling. Comparing 357 SIG vs. 38 Super using AA#9, which was the closest comparison I could find. Per Lee's VMD chart, 2400 is .0742 and AA#9 is .0657. So 2400 will fill the case and become compressed faster. AA#9 max in 357 SIG with XTP is 10.5 gr. compressed. 38 Super max is 10.7 gr. Alliant list a generic 147 gr. JHP in 38 Super max as 10.9 gr.
This is not an attempt to find an end all load. But merely an exercise to see what works. As I have plenty of 2400 and 300-MP for 357 mag.
Use with caution and understand, that this is an unpublished load. And in doing so, without any pressure test, the user of this data accepts full responsibility of any possible adverse effects.
Using a RMR 147 gr. Match Winner bullet, I worked up from 9.9 gr. to 10.7 gr. using 2400. RMR's 147 gr. is about .005" shorter than Hornady's 147 gr. XTP. The top loads are compressed. Winchester WSP primers were used. After reloading them, I realized that the 357 bullet is seated deeper (I believe by about .080") than the 38. My goal is to see which load would make between 1150-1200 fps.
So my plan was to get some velocity readings today. But for that one thing I always forget, today it was the tripod. And I couldn't get a good stack off a barrel at the range for a good chrony setup. So I shot the 1st 2 loads, 9.9gr. and 10.1 gr. No sign of primer flattening. The POI was the same as the 147 gr. XTP with 7.2 gr. of Longshot. About 1" to the right of the bullseye at 11 paces. Longshot was throwing the cases a couple feet further away. Without velocity readings, I won't go any higher. I want to make sure nothing erratic is happening.
This is not an attempt to find an end all load. But merely an exercise to see what works. As I have plenty of 2400 and 300-MP for 357 mag.
Use with caution and understand, that this is an unpublished load. And in doing so, without any pressure test, the user of this data accepts full responsibility of any possible adverse effects.
Using a RMR 147 gr. Match Winner bullet, I worked up from 9.9 gr. to 10.7 gr. using 2400. RMR's 147 gr. is about .005" shorter than Hornady's 147 gr. XTP. The top loads are compressed. Winchester WSP primers were used. After reloading them, I realized that the 357 bullet is seated deeper (I believe by about .080") than the 38. My goal is to see which load would make between 1150-1200 fps.
So my plan was to get some velocity readings today. But for that one thing I always forget, today it was the tripod. And I couldn't get a good stack off a barrel at the range for a good chrony setup. So I shot the 1st 2 loads, 9.9gr. and 10.1 gr. No sign of primer flattening. The POI was the same as the 147 gr. XTP with 7.2 gr. of Longshot. About 1" to the right of the bullseye at 11 paces. Longshot was throwing the cases a couple feet further away. Without velocity readings, I won't go any higher. I want to make sure nothing erratic is happening.
