Thanks for the advice I think the a400 is out of my price range. I think I'm
stuck on 3.5".(i feel like bigger is better and i dint mind the kick)I'll have to get my hands on some and see how the feel.
Come for advice? Pay attention to those who offer it. They typically have years of experience in the field, the range and with a multitude of different guns. When you come here with one post asking this question, it's likely you are lacking that range of experience. That's why you are here.
Bigger is most assuredly not better. 3" is plenty big enough. If you use it as an "all around" gun, we can assume you mean some hunting and some clays games. "Some" hunting, migratory, will require steel or other non tox. Upland and the clays games will not. The ONLY time there is ever a possible argument for 3 1/2" is when you are shooting geese with steel. And even then, it's not that good an argument.
There are a lot of myths in the shotgunning world. Often promulgated by ammo and gun makers. Damascus barrels will kill you. Steel is as good as lead. (that one didn't last long). Faster/bigger is better. etc. Not because they are true but because it helps sell more new product. I don't mean to pick on anyone but by way of example, there is another thread here right now about using target loads for hunting. Within the first page there is someone stating as fact something that is absolutely and demonstrably untrue. His post was immediately endorsed by someone else. One of the values of forums like this should be to clear away those misunderstandings about what is fact and what is myth.
I regularly hunt geese, waterfowl, upland. I never shoot a shell longer than 2 3/4". Ever. Now, I won't use steel and I'm not trying to convince you of the merits of that choice but my point is 2 3/4" and 3" will serve you well for everything thing you hunt. What is more important than chamber length is learning to shoot well. ie what you are aiming at.
The advice to try a multitude of makes is the best. A semi likely makes more sense for you than an O/U. Buy the best quality gun that fits you that you can possibly afford. Even if used. You will always get your money out of it and you will be happier with a better quality gun.