I’ve got a MK 60 20gauge away with BK Webster for a bit of a mod in terms of reducing stock drop and adding cast ( going up for it tomorrow ) . I shot it a few times before it went in . It’s only a 7lb gun , still has the plastic butt . With 21 gm CT clay cartridges it feels like you’ve loaded party poppers . Up it to 24 gm CT and it’s perfectly sweet , and if it ever gets an outing on clays that’s what I’ll use . Even with 28gm High Pheasant Supreme it’s not unpleasant at all .I was shooting an MK60 with a sold but pad. And I guess my gun mount is not always perfect
I find out of the box Miroku sporting guns a bit low in the stock , with them properly shouldered and my cheek firmly on the stock I’m not seeing much other than the back of the action. If you’re the same you might have been lifting your head and compromising the mount giving credence to the poor fit the guys above mention.