My favorite 243 load is a 100 grain Partition over the old style H4831.
The Interlock is a good substitution for the Partition, if that's what you have available.
It's nice if your powder about fills the case. A lot of people think that this tends toward accuracy. The old long cut H4831 just nicely fills the case with a 100 grain bullet.
I think that a lot of people get into trouble with the 243 by driving lighter bullets at speeds that cause cup and core bullets to break up. So a heavier, slower bullet is one answer to the problem. The TTSX probably also solves that problem, if you are inclined toward that solution.
