I would start by measuring your headspace. Some barrel/frame combinations can have excessive headspace. This will cause inconsistancy. It is possible to shim for excess headspace. Headspace should be kept to a minimum (.001"). I have seen headspace fits of .015". Also check for forend rubbing, especially where the forend overlaps the frame. The hinge pin can be taped into position; this will ensure it is not shifting side to side or rotating. This is basically what the locker pin accomplish.

If you choose to go to an oversized pin, the frame and barrel should be reamed to match the oversized pin dimension.

Also, check the tightness of the shoulder stock, I have seen a loose shoulder stock cause inconsistancy.