Franchi 48lL auto 6lbs4oz in 12ga even lighter in 20. If you buy the 12 get a 28" barrel and then have 4" cut off. You will be hard pressed to find a better gun for ruffed grouse. I personally have a Winchester 59 Winlite with 24" barrel, easy to carry and deadly. They are hard to find anymore and can be a little pricey. OU's are nice but if you are going to hunt where the grouse are it will get scratched to heck. My 59 looks like death warmed over has a big crack in the stock, also all the fisnish is worn off stock and forearm but keeps on shooting bagged 10 grouse in 3 days of hunting last week.
what gun to use??
