Hi Does anyone know what the twist rate for those rifles is? what is the best bullet weight that it likes? I'll be using mostly for yots and target. Thanks

Twist rate is 1:10 for a H&R - should be the same for the NEF.

85 to 95 grain bullets are the norm for the .243 with this twist, but each bore is different as well as the cartridge components. With certain combinations a lighter bullet may work well and with other components a heavier bullet performs best. If not reloading, try a box of several different weights, find the one that works best, then try the same weight with several different brands.