395 grains of black is about twice what I have tried beneath a quarter pound 4 bore ball. I would say that thing will have a definite kick.

Yes the big bore 'addiction' is both contagious and veral. 10 gauge and bigger. For me a gun I can carry is part of the requirement, though. The monster guns that you need a stand to shoot them from has no appeal to me. (Punts, etc)

Now that I have my four bore blunderbuss, I am looking at a 10 gauge (or even 8) double barrel that shoots modern shells.

Yes a 4 bore double (cartridge) is hopefully in my future. If I can get my company to start spinning off real money then I will start looking, until then it is a 10 (or 8) gauge double that I can pick up cheap and start fiddling with to shoot slugs using express sights, etc.