I haven't posted for a while, but wanted to add something here. Long story short:
My 12-year-old son is hunting elk for the first time this year, and though he has shot his 243 with cast bullets quite a bit, I swapped triggers a while back, and he has been using his 223 for hunting deer. To get him used to the lighter trigger, and have him use his 243 for both deer and elk, I worked up a load using IMR's old data easily found online using IMR 4227, since it mimicked the recoil of his 223 deer loads. IMR recommended 25 grains of 4227 to get to 2700 fps with 80 grain bullets. I found that 25.5 got me exactly 2700 with 80 gr Ballistic Tips. These shoot great in his gun (less than MOA) and it was a perfect performer on a broadside buck at just under 100 yds.
It also turned out that sighting in these loads at 150 yards put his elk load (100 grain Partition using 38.3 IMR 4166 to get 2950 fps) dead on at 225 yards. THIS is why I handload. Took some experimentation to get there, but the results are exactly what I wanted.
As an aside, I know the 80 grain BTs are the "Varmint" version, but they performed perfectly at their modest velocity, with an exit on a slight quartering shot centering ribs on entrance and exit that blew lung blood in a 2-foot line out the back. Deer did a 30-foot loop and collapsed almost exactly where he was shot.
