If you’re looking for a cheap semi auto 20 gauge, I just bought my son a Weatherby SA-08. They are all phased out except for the youth models, which you can find online at Buds for under $500. It functions just fine and has stock adjustment shims that can be used to fit the drop/etc better for an adult. It is not drilled for optics, however, but I bet you can get a set of Truglow front and rear fiber sights to fit that rail width. My son shot it with 3” heavy duck loads with no issue (he’s 11)