I built a tac 20 a few years back..it handles the 39 gr SBK really nicely...I finally got to a place where I could shoot it past 500 yds...& it was an eye opener...The bullet barely impacts the dirt at that distance!!!....We were comparing it to a 243 winchester using 88 grs of bullet...Anyone here use that bullet on varmints past 500 yds & would you reccommend it ???? I have my doubts about it in the Tac 20 case...When I built this gun I had pretty much decided it was for use up to 500 yds..Now seeing the bullet strike at 720 yds it was interesting..I dont think it would do a GH or a PD any good but it was not real impressive...mike in ct