Damn. I've never had this much fun finding the depth to rifling in my rifles.
My 7600 was just miserable... I think it's got a deep throat... but it's got a burr either in the throat, or in the lead of the rifling.
770... well, any gun that slams shut like they do doesn't give you much finesse to find the depth measurement.
In the end, I think the 7600 is about 2.23 to the rifling, while the 770 is 2.13.
I did find out too, though, that it's not worth loading the 770 longer than 2.8 oal because if you have to unload it, it doesn't want to eject shells longer than that.
blah