Maybe one goal, G.
The first GR sight I saw was when I was a teen, lo these many years gone.
It was a Lyman peep with the aperture removed, fixed on a obsolete Model 81 or 81 Remington autoloader in IIRC, 35 Remington. The owner had a long history of one shot kills with the thing.
My oldest 870 has worn one since about 1980, and it also is a Lyman peep sans disc. It keeps KO Brenekkes in about 4" at 100 yards from the bench even though they're keyholing slightly. Go figure.
That's from a 18",chokeless smoothbore barrel.
My bet's more familiarity with the system will see you tighten those groups even further.
Have fun....