Osprey,
I am very interested in your test results. My prediction however is that after 1000 rounds your model 12 will be just fine. The modern +P ammo is just not that hot! I would venture to say that the test loads S & W puts through the guns are a lot hotter than any +P we could buy. I have shot an older model 60 (no dash #) with plenty of 158 grain +P hollow point semi wadcuters, with no ill effect. The earlier model 60's like mine were not officially rated for use with +P ammo, but like I said, I have not seen any adverse effects on mine. I think this is a very worthwhile project!