My 10mm (with handloads) is a pretty heavy hitter in the semi world. My 44 mag (with handloads) makes my 10 seem pathetic. And Buck’s 460 can make my 44mag seem like a 10mm.
By some accounts a 10mm or .40 cal qualifies as “Big Bore”. Based solely on bore diameter starting with .4, this would be correct. But in MY opinion, you need the power behind the diameter, to make it to “Big Bore” status. And that status is pretty much reserved for revolvers that can handle the power.
Then you bring up the DE’s and my opinion gets negated somewhat. But there still isn’t a semi that can handle the power of the .460 or 500 S&W as far as I’m aware.
At the end of the day though, we’re shooters. If someone brings a .40cal or 357 to the range, I’m not going to belittle them or make their firearms seem inadequate when I bring out my 10mm 1911 and 44mag Redhawk. We’re going to have a great time swapping guns and ringing steel. And if they call their 357 a “Big Bore”, then so be it.