Well,

I was wondering exactly what is a "Snap Action" and it turns out that is is really quite simple. In fact, all of our comments above could be true because there were so many variations of Snap Actions, i.e, under-lever, top-lever, side-lever. Various makers who staked their reputations on one verses another would, of course, wish to discredit competing systems. Technically, Snap Actions are being used today by everyone. Whether one is actually more advantageous than another may be more theoretical than actual, but it sure does make for some beautiful guns and rifles

snap-action
From: The Oxford Essential Dictionary of the U.S. Military | Date: 2001 | Copyright information
snap-action adj. denoting a gun whose hinged barrel is secured by a spring catch.

It still leaves a few questions regarding the original description, but this may at least answer one of them.