Firstly i'd say don't go out and try all different types or brands of ammo, stick with one. The hornady v-max are inherantly accurate So i would start here.
Secondly keep the mod of for the test, my 243 has lost all accuracy with it and i dont know why, So off it's going to stay, its one of the first t8's out, and has it's time served.
thirdly, give the barrel a good cleaning, i fed the .243 cheap ammo and ended up with three hours cleaning to get the copper out, of which i never had a problem with before as i always kept it in check.
but to my amazement it was full of copper fouling after