I would start with the basics, make sure the scope rail is mounted securely, the screws are loctited in place, check to make sure the rings are tight, also. Have the guns been cleaned real good inside and out from the start? Make sure there is no lubricant on the latch and latch shelf so the lockup is always the same. Make sure you pull the trigger fully to the read at each pull, don't release pressure at the break, the transfer bar safety mechanism will prevent full impact on the firing pin if you don't which can lead to inconsistent accuracy. All of my H&R rifles like to be shot dirty, clean barrels aren't as accurate until they've been fouled by a few shots. This is just a start, read a lot here and you'll pick up some more tips....
Tim