I've never been duck hunting but I've been invited to go this year. The only shotgun I have is a Mossberg 590A1 with a 20-inch barrel, cylinder choke. I don't have the funds to pick up another shotgun or even a spare barrel so this is the only shotgun I'll have. What can I expect? Are there certain loads that will give me a tighter pattern out of what is essentially a tactical shotgun? Maybe Federal Flitecontrol? Also, what are some recommended shot sizes for duck? Thanks in advance for any help.