I have a Tasco 6-24x44 with fine crosshairs and an 1/8 dot reticle. Works fine for me and my varmint control.
You will find most H&R/NEF 223's like the lighter grain bullets due to the rate of twist. The Winchester White Box 45gr JHP usually shoot the best. So you might want to give a heavier bullet a try, but I wouldn't expect too much. My Ultra hates the heavy stuff, but feed it some WWB 45gr and it does the job over and over.
EDIT TOO- originally I though it was a 223? I guess the author changed it.