With the Handi Rifle, they can be very sensitive to trigger squeeze due to the transfer bar system. Another thing that they are sensitive to is forend placement. More so than any other gun I have shot. I have 3 frames and 5 barrels, all of which will shoot MOA or better at 100 yards.
If I just flicked the trigger like my varmint guns, I would get a larger group than when I exaggerated the trigger squeeze and held the trigger back until the gun recovers from recoil.
The design of the forend makes this rifle sensitve to forend vibration transfers. I pillar bedded my forend and use a rubber O-ring around the forend retaining screw to deaden the vibration transfer. These two things made the largest difference in group size for my Handi Rifles.
Good bench technique is also required. Watch the downward force of the trigger hand. It can flex the buttstock to action junction and cause problems for groups.
Be sure to check the scope mounts. They can work loose.