I own one of these shotguns for home defense. It is not suitable for hunting. State and Federal laws require that shotguns be limited to 3 rounds for most types of bird hunting. I know of no one that has made a plug for the FN SLP-1 to limit it to 2+1 rounds. If a wildlife officer stopped you and examined your gun, it would definitely be confiscated, and you would be cited.
The gun is quite heavy too, so it would be a pain to carry in the field. The short 22" barrel also makes it more difficult to shoot accurately. Long barrels on shotguns give you more momentum for a smoother swing. The shorter barrel length also means greater muzzle blast, which will damage your hearing more.
Sporting shotguns should be at least 28" long, or even 30" That is what I hunt and target shoot with.
A far better general purpose shotgun for you would be the latest Beretta Model 391 Urika II semiauto. It has an amazing gas system that is super reliable, a chamber and barrel that is chromed for ultimate durability, a fantastic trigger pull, and a most comfortable stock with high tech surfaces on the stock to enhance your grip.
And I know a dealer that I do business with who currently has them on sale for $200 off their normal price, for only $699 That is quite a bit less money than the FN, and you will have a much better shooting shotgun.
Here is a link if you want to checkout his Beretta 391 Urika II sale:
http://gunbroker.com/Auction/ViewItem.asp?Item=131908033
Here is a photo of my two sporting shotguns. They are a Beretta 391 Urika Gold Sporting Edition ( on the bottom ), and a Beretta 391 Extrema 2 ( on the top ):
And here is a photo of my FN SLP-1:
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