I am doing 100 yard .357 Magnum target work with my S&W 684 (4" barrel). I started out using 10.0 grains of AA#5 with a Hdy 125 grain HP-XTP bullet. I used the Accurate Powders loading manual as a reference, which shows 10.4 grains as a starting load, giving 1369 FPS velocity from a 6" barrel. My 10.0 load chronographed at about 1140 FPS and gave consistent good groups at 100 yards. I use a T/C 2.5-7 power handgun scope. With this load there is no indication of excessive pressures (spent cases eject easily).
To explore higher velocities I shifted to a slower powder (AA#7) using the same 125 grain bullets. Accurate lists a starting load of 11.9 grains (1374 FPS) and a max load of 13.2 (1562 FPS and 42,700 psi). I loaded in the middle at 12.5 grains and chronoed this at 1350 FPS. But, I stopped shooting after only ten rounds because my spent cases were sticking hard in the cylinder chambers. So hard that I have to really smack the ejector rod to get the cases loose. Primers don't look all that flattened, but clearly there is a overpressure problem. By the Accurate book, there surely shouldn't be, and by the measured velocity there shouldn't be too much pressure.
Of note, and very confusing, the Hornady Handbook lists the max load for AA#7 with their 125 HP-XTP as 11.5 grains, giving 1400 FPS from an 8" barrel Colt Python. No pressures are listed. Any ideas and advice would be appreciated. It may be that the supposed very light load of 10.0 AA#5 turns out to be the best long range target load, but the drop is 6" from a 25 yard zero, so I would like a higher velocity to have less drop and less effect from any wind. Looking at using the 158 grain bullet in the future but with this problem, I don't dare go to a heavier bullet until I figure out what is wrong.
Thanks.
To explore higher velocities I shifted to a slower powder (AA#7) using the same 125 grain bullets. Accurate lists a starting load of 11.9 grains (1374 FPS) and a max load of 13.2 (1562 FPS and 42,700 psi). I loaded in the middle at 12.5 grains and chronoed this at 1350 FPS. But, I stopped shooting after only ten rounds because my spent cases were sticking hard in the cylinder chambers. So hard that I have to really smack the ejector rod to get the cases loose. Primers don't look all that flattened, but clearly there is a overpressure problem. By the Accurate book, there surely shouldn't be, and by the measured velocity there shouldn't be too much pressure.
Of note, and very confusing, the Hornady Handbook lists the max load for AA#7 with their 125 HP-XTP as 11.5 grains, giving 1400 FPS from an 8" barrel Colt Python. No pressures are listed. Any ideas and advice would be appreciated. It may be that the supposed very light load of 10.0 AA#5 turns out to be the best long range target load, but the drop is 6" from a 25 yard zero, so I would like a higher velocity to have less drop and less effect from any wind. Looking at using the 158 grain bullet in the future but with this problem, I don't dare go to a heavier bullet until I figure out what is wrong.
Thanks.
Last edited:
