Is it common for manufacturers to make rifles that are not listed in their catalogs? I sometimes see a certain rifle model chambered in a caliber that the catalog does not show in that caliber. Are these discontinued models or just short runs the manufacturers do on a whim?

They're most likely discontinued models. Like my Remington 514 .22S,L,LR bolt-action.

It's more likely a previous year's carryover. I've bought new rifles that are over four years old.

I know Remington makes some calibers / models not listed even when they are a standard offering. For example, the 673 Guide gun listed in .300 SAUM and .350 also was offered in .243 and .308 but not listed. I found this out by asking.

Mike

Gun makers will often make a special run of a non-cataloged rifles for a certain distributor. For example I own a Ruger M77 30-06 in stainless steel with a black walnut stock that was made for a local distributor (Never cataloged)
I have been looking for a "special run" Remington ADL synthetic in .257 Roberts that was also specially made for a PA distributor.
To answer your question...............This is common practice especially in my neck of the woods.
Encore28

Encore28 is exactly right. A distributor that is willing to order enough rifles can have just about any configuration that he is willing to pay for. I have a Remington 700 Classic Stainless chambered for 257 Roberts. This is just one such example. I have also seen at many gun shows the Remington 700 ADL synthetic in calibers such as 257 Roberts, 25-06, 280, 300 WSM, and several other calibers not listed by Remington.