What do you think is the average weight for a 3 season bag for backpacking? Let's say a 20-30 degree bag. To me it seems like right around 2.5 to 3 lbs. I'm trying to get into a new bag this year.
I would look at WM and Kifaru slick bags. If your looking in the 30 range there are some sub 2 pounders.
I have the Montbell U.L Super Spiral Down Hugger long #1 15 degree bag. I just weighed it came in at 2lb 5oz.