He said he shoots trap and skeet (generally pre-mount games), and rarely hits 50% with these guns.
He shoots left handed with right handed guns.
There has to be aiming error, and in-effective technique involved, not just gun fit.
The angles and leads of American skeet are well known. Sight pictures get memorized.
People shoot high scores from the hip as example.
Many people cover up aiming error with heavy loads of small shot and choke boring.
All of which complicates building a good consistent score across the gauges.
I generally fuss with the comb at face and cheek using removable foam.
Then start at the shoulder pocket as an anchor point for pre-mount games. The foam sets the cast, and eye alignment.
If you build the foam up to get 50/50 vertical patterns, then the misses are errors along the flight line, ahead or behind.
You can push the barrels left or right by adding or subtracting a piece of material.
If your pattern board alignment is 50/50 concentric, then it’s your foot placement and swing.
In a 12, you don’t have to be that close at 22 yards on a skeet field to get a break.
But you need to see a site picture where you are in front.
On the in-comer’s taking them well out is a cheap fix for low 1, low 2, high 6, and 7.
Bigger pattern when shot from across the field. Covers up aiming error.
Presuming one uses the standard maintained lead method. And starts ahead to stay ahead until the site picture and swing position connect.