The A400 uses chokes with the OBHP thread system and not the older thread systems that Beretta has used. Beretta states that those barrels are "slightly over-bored" and for Beretta that's usually about .733 or so. I have not personally measured the bore on any of them.
Everyone that I know or have spoken to who has one really likes the gun and they are of course beautiful guns, well made in the Beretta tradition.
Thanks,
Clark