The problem, eightbore, is the definition of "a reasonable load" for the gun in question. Seems everyone is missing the very critical chronology issue to which I earlier made reference: SAAMI was not established until 1926. Therefore, prior to that time, there were NO COMMON STANDARDS for the proof of guns in this country; no common standards for the proof of ammunition, nor the establishment of service pressure ceilings. I submit that, therefore, there was no definition of "a reasonable load" for all shotguns being marketed in this country prior to that time.
In other words, what was "reasonable" for a Parker, Lefever, Elsie, or Fox would not necessarily have been reasonable for a Long Range Wonder bought down at Acme Hardware. Unfortunately, lacking both a national proofhouse or a voluntary organization of arms and ammo makers (that would be SAAMI), Great Grandpa George Sixpack had no way of knowing what he ought to be shooting in his new gun.
The creation of SAAMI came about at a very critical moment in the history of shotguns and shotshells in this country. In 1926, the new Super-X was just hitting the market. That shell was longer (2 3/4" vs 2 5/8") than the old standard 12ga chamber, and hotter than the then-standard 12ga loads. So . . . we start with the fact that there weren't even any common proof and service pressure standards for the old 2 5/8" guns and ammo; add to that a longer, hotter load. (Ithaca had even switched to a newer, stronger design for its doubles--the NID--to deal with the newer, hotter loads.) It's at that point that the arms and ammo makers get together and say "OK, this proof level and service pressure are reasonable for 2 5/8" 12ga guns; these higher levels for 2 3/4" guns."
Think of this somewhat like OSHA--which, in spite of all its stupid excesses, manages to keep some idiots from harming themselves every year. Same deal with SAAMI--with a somewhat lower level of excesses. What SAAMI had printed on 2 3/4" ammo boxes was "Don't use these shells in guns with Damascus barrels, or in guns with chambers shorter than 2 3/4". Overkill? Yes, to a certain degree. But their view was, better to err on the side of caution. Sure, we know that some Damascus guns will handle smokeless powder loads (at proper pressures), and 2 1/2" guns will handle 2 3/4" hulls (at proper pressures). But the kicker is that the higher proof and service pressure levels for 2 3/4" FACTORY loads meant that they were not appropriate, either in most Damascus guns or guns with short chambers (which had different and lower proof and service pressure levels). And we also have to remember that back then, there were quite a few cheap, imported guns (many with Damascus barrels) that could not take the same loads as a Parker, Elsie, or Lefever--much less the new, hotter 2 3/4" loads. Or could not take them without wearing out in a hurry, or maybe worse.
That puts us where we are today. Thanks to those SAAMI standards, we know that we can take any new American-made 12ga with chambers 2 3/4" or longer, and we can shoot any American factory 2 3/4" load in that gun. We have that level of confidence because we have standards. And that level of confidence means that Joe Sixpack in 2009 is one whole heck of a lot less likely to get himself into trouble by selecting inappropriate ammo than was Great Grampa George Sixpack back in 1909.
But it stilla means that those of us shooting shotguns handed down to us from Great Grampa George--such as 12's built with 2 5/8" chambers, well before WWII--ought to be fed a steady diet of FACTORY 2 3/4" shells that exceed the velocity and shot charge levels established as standard for those guns by SAAMI. As for pressure, we don't know whether specific FACTORY 2 3/4" shells exceed the service pressure ceiling established for 2 5/8" guns--but we do know that the current SAAMI service pressure ceiling for the 2 3/4" 12ga is higher than it was for the 2 5/8" 12ga. So there's a very good chance that current factory shells are also overpressure in old, short-chambered guns.
Summary: You can say "My Parker (Fox, Ithaca, Elsie) whatever with short chambers has digested x thousand modern, 2 3/4" shells, and it's as tight as when it was new"--which is great, but which is relevant only to YOUR SPECIFIC GUN. It's what's called "anecdotal data". Because the next guy's gun might shoot loose--whether due to pressure or recoil we can continue to debate, but regardless--after having undergone the same use. If you want to PROVE that your gun is good to go with any 2 3/4" shell now made in this country, here's how you do it: submit it for proof at 19,000 psi. If it passes, continue to blaze away. But unless you do that, reasonable caution would seem to dictate that you ought to use shells loaded to no greater pressure, velocity and shot charge than were available on the market AFTER SAAMI came into existence. Those standards are known. For the 12ga, it's particularly easy to reload within those standards. Or you can buy shells loaded within those standards.
Unless someone has particular questions on this subject, that's where I stand.
