Like I said it was designed to give the gun better reliabilty with a greater variety of loads but it was never designed to make the gun reliable with all of them. Lighter loads will operate the gun without a doubt but it will never be as reliable as when the heavier ones are used.
The actions of semi-automatic firearms are designed to operate at certain speeds. If you exceed those speeds reliabilty suffers. The same thing happens when those speeds become too slow. On gas operated guns that is where the self-adjusting gas systems comes into play...trying to keep the action speed in its optimal range. The problem with most semi-auto shotguns, when firing magnum loads, is that the gas systems can't bleed off enough gas fast enough to keep the action from exceeding the optimal operating speed. To help slove this problem and prevent premature wear and parts breakage the designers use a heavier recoil spring to assist in slowing/cushioning the rearward action travel. This directly interferes with light/low recoil load reliability. That is the case with most semi-auto shotguns that were designed for hunting. Target specific/oriented guns seldom see use of magnum loads (also why many only have a 2 3/4" chamber) so generally use a lighter recoil spring which ensures the action speeds stay in the "sweet spot" with the softer shooting/lighter recoiling target loads.
As for the loads I recommended for the 11-87...I got those from experience. That experience has also revealed that the Remington 1100/11-87/11-96, although great guns, have a very slow actions. For fast shooting I find myself waiting for the action to cycle before I can pull the trigger again. The same thing happens with the Beretta and Benelli guns. I don't have that problem with the Browning/Winchester siblings...but they must be kept ultra clean to maintain reliabilty!
