My 16ga Halifax has a 5 digit SN, 49505. On it while the extractor is spring loaded it also is engaged by a 90° bent lever which projects under the vertical locking bolt. As you raise the key the bolt drops, contacting this lever which cams the extractor out & also starts movement of the breech block. I have never had a problem with this gun extracting any normal shell, plastic or otherwise. Matter of fact have only used plastic in it. It is marked with a #4 which I assume is a grade.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra