Looking for advice on a bird gun.

Why don't you buy a barrel and plug for your 500, shouldn't run you much more than $100.

Or go to Bi Mart and pick up a new 870 express for $230 (on sale). Since you live in E Wa I know of two in the Spokane area. Will be an excellent shotty and you can change whatever you want on it.

I have a old wingmaster that only takes 2 3/4" shells and doesn't take different chokes that is a great bird gun. I don't know anything much about the new 887 but I think the wingmaster is tough to beat. Plenty duck, pheasant, quail, and dove have been killed with 2 3/4" shells and plenty more will be. I think the 3" and 3 1/2" shell are more for geese and turkey YMMV good luck picking a gun.

Having different chokes can be useful and the longer chamber on the 887 would probably be better for duck hunting with steel shot. I'm pretty sure the Wingmaster is nicer looking though and it would do the job.

If you already have a Mossberg 500 6-shot, getting a longer barrel would be a good option.
http://www.midwayusa.com/viewProduct/?productNumber=227387

The most important thing for bird hunting is that the stock fits you. If you're not looking right down the barrel when you throw the gun to your shoulder, you probably won't hit many.

Big R - Dookie’s advice on getting another barrel would be the way to go because you are already familiar with the Mossberg's operation and used to the fit of the stock

I’m guessing that you were already aware of that because it sounds like you are itching for another gun in your armory. So...

That Wingmaster you were looking at in as-is condition is not the gun you need for hunting the birds you mentioned because all of the early season birds will decoy or fly closer to you than late season birds that have taken hunting pressure and are now more leery, therefore, a fixed choke is a detriment. However, if the price is right and you’re willing to spend the extra bucks on another barrel with screw in chokes then that might be the way to go.

Long ago I lost count of the number of ducks, quail and doves I’ve harvested with 2 3/4" shells and never felt under armed when the use of lead shot was allowed. Today’s restriction to non-toxic shot may necessitate going to a 3" or better chamber to get to high flying ducks (~ 55 yards or less - choke dependent) and those that will not be decoying closer in the late season. For ducks in the late season I put up my Rem. 1100 and break out a S&W semi-auto with adjustable chokes and a 3" chamber.

I have zero experience with the 887, so I can’t comment on it.

The Wingmaster recommendations were based on a 12 gauge (you didn’t mention which gauge) and this warning about the Remington wood stocks - late model stocks may be okay, but all the ones I’ve bought were not sealed against moisture under the butt plate. If you get one, remove the plate and seal the wood - if the gun is going to be around water or in the rain and it’s not sealed the wood is going to swell and crack - ask me how I know...

The 3 inch and 3.5 inch guns were mainly made to accomodate steel shot loadings for waterfowl when lead was banned from waterfowl hunting. Steel is less dense than lead...

Steel shot tends to blow open it's patterns if over choked. So unless you are using a special shot tube for a full choke (like a trulock or something) then you'll probably be shooting an improved cylinder or modified over decoys. You interchangeable chokes will say which ones are ok to use with steel stamped right on them.

If you plan on only going waterfowl hunting once...like one or two times, then you might be better off just buying some bismuth or heavishot and using your 2 3/4 inch gun. It shoots like lead but costs like 5 times as much.

The main thing with waterfowl hunting is...your gun will get wet - really wet eventually. Like you could literally have to use your gun for a paddle, or an underwater support to get your sucked in frozen wadering buddy out of a muddy sink-like hole, or you'll have a sling on it and the stock will be dipping in and out of the water as you set decoys, or the dog will shake itslef off by you or...well you get the point. You want a gun that is easy to take down for cleaning. Then none of the above is a big deal.

If you happen to go waterfowl hunting, I hope that you're cold and miserable and hate it...because if you like it...it becomes a year round addiction that will make you start id'ing every bird on a lake regardless of month, start researching dog breeds that are compatible with the wife, buy/make a dedicated boat, gun, decoys, waders, and boat blinds and layout blinds. Practice hail calls and clucks on the way to work. While other people are talking about what was on tv last night you'll be telling them about duck commander videos or new ways to carve your own decoys. It is really awesome. Once you hear the whistling wings in the decoys....