I think most of us on here do shoot a wide variety of MLs Grouse. But I don't know what kind of testing you do to get unreliable ignition. And a bit of blow back from a shot or two during a day of hunting is definitely no problem. At least for me and many other shooters. And I don't want to start an argument but the way you must do your testing has absolutely nothing at all to do with hunting with a ML because I don't think anyone shoots as many shots at all the game you stated in one, two or even a week without cleaning their rifle.
But out of curiosity, what do you find unacceptable with the breech plug in the CVAs?