That is a very promising group!!! And with a front bead and NOT express sights. I would say you mots likely have your double barrel slug gun there. You are on your way. Congrats!

And as you probably figured you want a rear express sight that you can adjust LEFT/RIGHT as well as UP and DOWN. It makes all the difference.

Also, I found the same as far as recoil... the Brenneke's were not bad at all, but those Winchesters serve up a hard sharp kick.

I really enjoy when people actually TRY out their double barrel shotguns with slugs... Most times the results are the gun is definitely a shooter at 20-25 yards and often even at 50+... And off-hand!!!! which is how most shots will be made in the field. Anxious to hear more on this double of yours and the progress to make it a double barrel slugger with TWO sights!