Well JMC, I would be considering a law suit against a gunsmith that deepened chambers without express instruction to do so. It ads no benefit, I mean zero, and it removes metal from the most critical area of the barrel. It won't cause harm if the barrel wall was thick enough but no way of knowing that unless it is measured. Getting an accurate measurement right at the end of the forcing cone and just beyond it so as to know exactly how much metal you have to work with is a lot harder than just running a reamer, which any fool can do. Remember that the walls of the chambers on the side that adjoins the other barrel can't be measured. That's a judgment call made by guess work. I can't believe how often people do it, even reputable gunsmiths, without any mention of reproof. I don't think that any reputable British gunsmith would do it without reproof.
