For example, while it's not clear what model this UTG is modeled after, many say it's somewhat like a Benelli. That said, now think about reloading. There's no port on the right side of the gun, and the 'tube' can only accept 1 shell by loading it underneath. Conclusion: probably not the best gun to use if you are working on learning how to reload something like your real Benelli.
Here's a Mossberg clone. Looks-wise it's pretty good, but again, there are training issues that will come up since this one takes a mag and not shells.
NOW, here's an example of a gun that might work, at least a little better. This shotgun loads 2 shells at a time and the shells are very similar in size to a real shotgun shell. While not many people have this kind of 'pirate gun' in real life, the concept remains. If you are going to use an airsoft gun to work on training and reloading, make sure it's as similar as possible to your real-steel gun.