i have been shooting BPCG for a loong time,,and i have 4 hiwalls and 2, 74 sharps and a 75 sharps
i am not a great shooter but i do have some desk art and some wall art from the range
if you listen to what NoSecondBest has told you it WILL come together for you
these hiwall guns are VERY pressure sensitive,,,to much head pressure on the stock,,,to much barrel pressure,,,it all comes down to shooting and finding the magic sweet spot,,,that means pressure you are putting down on the gun
my meachum gun with 34" barrel likes the cross sticks about 2-2 1/2" in front of the forearm,,,my browning 30" barrel likes them right in front of the forearm,,,but it is shorter and has a hex to round barrel and that cut makes the harmonics way different
also the twist of the rifling will sometimes dictate what weight bullet the gun likes,,,most of the big guns 45 cal. have a 1-18 twist,,,and they like the heavier bullets 500-550gr,,,not always but most times
i have a browning traditional hunter little lighter gun but still a hiwall,,it has a 1-20 twist,,,about 425gr bullet is where accuracy starts going away,,it really likes the 380gr small gov. bullet
i will add that if you are going to shoot from the bench and you are going to use bags for support,,,,put you hand on the forearm just like you would be shooting the gun and put you hand on the bag for support,,,ie,,,bag,,hand ,,gun,,,,and try and keep the head to stock pressure the same shot to shot,,,,it will as NoSecondBest has said "make a big difference",,,,you will see the difference
when it all comes together your group should be in a circle,,,,stringing vertical or horizontal is telling you something,,,,,"hey i dont really like this you need to change something"
just some thought and my .02
ocharry