As a regular method for trap shooting, can 12 gauge pump action Winchester Model 1897s and IAC (Norinco) 97 clones be loaded by dropping a shotshell through the open ejection port, then complete loading the chamber by sliding breech bolt forward to lock it? I ask because I have been told there are some pump action and semiautomatic shotguns whose extractors will break by regularly loading in this manor.

could be .. i've never seen this as as an acute failure mode ... though, honestly, when i am shooting skeet, i go through many rounds in a day

thats the way the do it in cowboy action shooting

I've had zero issues over the years loading a couple of '97s "over the top" shooting Cowboy Action. Fast '97 shooters in that sport do so exclusively...Google some Cowboy Action videos and watch them run a '97 loading from a fistful of shells in their left hand.

Mark

When you drop a shell into the ejection port of a M97, M12, it falls down upon the carrier.
Thats the same location and position a 'next round' out of the magazine would feed and end up positioning itself.

Closing the action simply lifts the carrier up with that round on it (wether you dropped it in there or the magazine deposited it onto the carrier).
The round is nose first tilted up towards the chamber. The back end is high enough so the now closing breech block can begin to push it forward and into the chamber.

In doing so the rear end of the shell slides up the face of the breech block and the rim of the shell slides in behind the extractors.
(Controlled Feed)

The extractors do not have to flex outward over the case rim...they barely exert pressure on the rim from the sides.

Dropping a round directly into the chamber and closing the breech does make the extractors flex/ pivot and snap over the case rim.
The extractors are coil spring powered here, but some shotguns use small flat springs. The shape and size of the extractors vary in different designs and some are not as strong as others.
Making the extractor go full flex and pivot to snap over the case rim is just making it work more.

As with any part,,they can wear out and break. It doesn't matter if it's a Winchester, Meriden or a China made import.

My question has been answered clearly.

Many thanks for every one of your replies.