Interesting article perhaps.

Not a particularly good one.

The misquote of MM likely should be attributed to O'Connor.

If you can make recoil operated guns work with a specific lower pressure load, you likely can make a 391 work with it also. Lower max chamber pressure does not necessarily translate to lower pressure at the barrel tap point on a gas auto. 7,000 psi is not an absolute, and I know of at least two 391's in regular service with 7/8 oz target loads which have pressures below this often quoted minimum for reliable functioning. Supporting pressure curves are posted here with some regularity.

Too bad that any article like this now has to be so full of lawyer-speak. That takes away most of the pleasure of reading it.

"The price of good shotgunnery is constant practice" - Fred Kimble