I did dig up this note from "
lei...@googlegroups.com" from Dr. Rivka Sherman-Gold, author of "The Ohs and AHS of Torah Reading: A Guide to the Kamatz Katan in the Torah, the Haftarot and the Megillot"
In a few instances, a Kamatz “accompanied” by a meteg and followed by a Shva is actually a KK and the Shva is NaH! Examples:
שָֽׁמְרָה (Tehillim 86:2), רָֽדְפִי־ (כתיב רָֽדְופִי) טֽוֹב (Tehillim 38:21), and עֲמָֽדְךָ֣ (Ovadia 1:11),
(Yes, I know that Tanakh Simanim shows these words with a Kamatz Gadol followed by a Shva NA, but Simanim follows traditional Sephardi reading, whereas in Normative Hebrew it is a Kamatz Katan. In fact, not all Sephardi grammarians agreed that these unusual cases of a Kamatz with a meteg is a Kamatz Gadol.
The identity of a Kamatz depends on the word’s grammatical form, not on the presence or absence of a meteg. The Masoretes who “invented” the meteg did not use it to indicate the identity of a Kamatz as Gadol or Katan. They used the same vowel-sound for each Kamatz vowel-sign and didn’t need a device to differentiate between two types of Kamatz, which was not part of their pronunciation. The concept of
Kamatz Gadol and
Kamatz Katan was introduced by post-Masoretic Sephardi grammarians based on their own pronunciation, which differentiated between two Kamatz vowels. They needed to reconcile their Pronunciation with the Tiberian-Masoretic Nikud. The Masoretes used a meteg as a tool for phonetic and rhythmic reasons.