There a couple of things to consider that might have been missed. A rectangular post front sight is superior to a round bead in that it provides an index of elevation. The flat top of the post equates to the horizontal wire of a scope's cross hair, and the eye easily discerns the center line of the post, which equates the vertical wire of a cross hair. Viewed against a round bulls-eye target that subtends to the width of the post at the range your are shooting from, its easy to find the center of the bull, since the width of the sight will appear wider in any other position on the target, thus groups are smaller since there is less vertical sighting error under conditions of consistent light. Bright sunlight tends to burn out the height and/or width of the front sight, and a good rifleman must be cognizant of this.
The thin rim, large aperture rear ghost ring rear sight is superior for field shooting than the thick rimmed small aperture target sight, even though the smaller aperture improves one's focus of the target. Focus should be on the front sight rather than the target anyway, and since the ghost rings blurs out of your perceptible view (hence its name) you don't attempt to consciously or subconsciously center the front sight in the visible aperture, so your shot is made faster, with little precision lost. This is important due to the open ended timing of field shooting, you don't know how much time you have to make the shot, so you must shoot as quickly as you can shoot with precision. Simply acquire your sight picture, shift your focus to the front sight, then press the trigger. Provided your cheek weld on the stock is repeatable, with a little practice your groups will become pleasingly tight.