The problem I found with .243 Winchester as a precision round is that it almost requires handloading, not because the round or rifles chambered in it are particularly finicky, but because factory ammunition is either geared specifically toward varmint shooting or deer hunting. Both of those will do okay, but, with very few match rounds available, okay is all I would reasonably expect. It's kind of like .260 Remington and 6.5 Creedmoor. They're basically the same round once the bullet leaves the barrel, but the .260 has spent most of its life as a deer round whereas the 6.5 Creed was either purpose-built for or was perfectly timed to take advantage of the precision rifle fad. With the rise of the 6 Creedmoor in addition to the 6.5, the demand for factory. 243 Winchester match rounds might dwindle further!

Cool project so far! Keep us posted on your progress. You say you did the poor man's trigger job: is that just the trigger spring replacement and overtravel screw or did you do anything to take the creep out?