they sure as heck aren't going to make one using the old open frame design - and not because of cost.
Jim:
Are you serious? Cost is the first consideration in any build of anything.
I am not talking cheap, I am talking cost of a given design you are trying to industrialize. Higher cost is only justified by having to go to higher cost to meet a performance specification.
Now I know some are now saying, ah hah.
But....... when you have no background in Open top and all your background is in a Top Strap?
Research is costly. You don't know if an Open Top design would work, but you know you can beef up a Top Strap design (or so says your CAD). So you go with that because it is lower cost.
Now, say the 500 S&W came out weighing as much as the Anchor on the Queen Mary. Ok, full stop, do we continue (not with these materials). Can be do it with Unobtanioum? Yea we could, but then the price of the gun is $100,000 a pop. Not selling that are we?
So now its, maybe we should pare this back or forget it! Well, there is that old Open Top design no one explored further, what if we research that? How much is that going to cost? And we don't know its better, equal or worse until we do.
Jet engines come to mind. They use some cutting edge exotic materials (composites as well as metals). But they get efficiency, longevity etc out of the engines (and reliability) and its worth it.
In WWII the Germans got 50 hours of life period out of their jet engines. Its impossible to keep 100 ME-262 in jet engines (200) if you eat one up every 50 hours and that was average, some failed much sooner.
In their case, they had no choice. The were cut off from sources of exotic materials and they had no alternatives, so cheap engines it was (they were indeed cheaper than a piston engine). But it never cammed over to a real advantage as they never could get the numbers to do so.