Even low recoil 20s will have substantially more free recoil than a 2.5 inch .410 load....even when the .410s are fired in a lighter gun.
In either case, we are not looking at big figures....a bit under six ft.lbs FR for the .410 and a bit over nine for the low recoil 20s. Five and six pound guns, respectively.
Thank you for the numbers. Well with that recoil difference, if one shot a 20 gauge semi-auto then should help even the recoil.