05-20-2018, 01:41 AM
It sounds like your hand-loads are not giving enough gas to cycle those guns, so undergassed.
Looking at Quickload I can see that while 8208 is giving you high peak pressure by the time it gets 10" down the barrel to where the port is it has dropped more than other typical powders used with the 123SST. I would keep 8208 for bullets under 120gn and use something like H4895. It will also give you a lower peak pressure for the same velocity, and your gun will thank you for it.
Looking at Quickload I can see that while 8208 is giving you high peak pressure by the time it gets 10" down the barrel to where the port is it has dropped more than other typical powders used with the 123SST. I would keep 8208 for bullets under 120gn and use something like H4895. It will also give you a lower peak pressure for the same velocity, and your gun will thank you for it.