A LOT of things came from the factories sometimes, and sometimes they never saw any action period. Just saying "they came from the factory" means nothing. Look at the USN example of -Ps, they came from the factory with 20mms installed but there's next to no visual proof that they ever used them. In fact there's an abundance of proof to the contrary. A lot of -Ns also switched to all 50cals, also.
Simply saying "It came from the factory" is wishful thinking in this case. We can go back to the Spit Vc with 4x20mm example again, too. It's been rehashed many a time.
What does the Fairey Gannet (ugliest plane ever designed in WW2) have to do with F6Fs' armament?
Oh, and just saying that the brits had the belt links means they used the ammo is a spurious claim. You need to go one step further.
Like I said, if there's supposedly almost a thousand of these planes in service there would be photographic proof.
As noted in one of the longer previous 20mm-on-hellcat-posts, I noted that about half of the -Ps were supposed to go to the Brits, but were diverted to the pacific. They never got there in time, and at war's end were shoved overboard into the sea. That alone would account for a large number of them. Still, with about 400+ of these around, there should be SOME photos, right? I haven't seen any. If you've got some post them.