I currently have a Winchester SXP 20 gauge pump that I'm using. Looking to potentially upgrade to a semi in 20 gauge specifically for Turkey hunting. Looking for something light, with a better trigger than the SXP, and a gun I can easily mount a reflex red dot on.
I like my Retay Masai Mara XT...super light. I haven't shot the Winchester SXP so I can't compare triggers but I have no issues with mine. It also has a picatinny rail system that you can easily mount a red dot on. Sumtoy also makes lower profile mounts that will fit the factory holes if you want to go that route.
I personally have no experience with them but a friend of mine who hosts a well known outdoor tv show is shooting the Mossberg SA-28 Tactical Turkey this year and he absolutely loves it...and he hunts birds all over the place.
I have a Tristar Viper G2 Turkey that I just bought. It's a little over 6 pounds so that should meet your weight requirement. The trigger wasn't the best when I got it so I installed an M-Carbo spring kit that was around $10. It brought the pull down to just over 4 pounds. It comes with a picatinny rail so mounting a reflex site shouldn't be an issue. Mine is fully Cerakoted and has a chrome lined barrel which I really like.
(https://i.imgur.com/0JCeYvxl.jpg)