This is a question which has crossed my mind for years yet I've never asked it. Why, I don't know why.

Concerning the Rem 700 short action and the calibers which fit, or don't fit. What measurement is it which determines if a cartridge will fit into a short action? Take 308 based cases; 243, 260 Rem, 7-08, 308, 338 Federal, 358 Win (did I miss any?); In looking at published data here and there, I see 2.800", or slightly more, as max for these cartridges. If a cartridge is .1", .2", .3", etc longer than 2.800" will it not fit the magazine or not eject if unfired? So, I guess I'm asking what will happen if a cartridge is too long for the action?

I think your reasoning along the right path. An actions length limits the length of the cartridge that will feed, chamber and eject through the action. If the rifle is to be used as a magazine operated action, the cartridge length is critical to the above mentioned functions. If the rifle is to be used as a single shot then the cartridge length is less critical. The very fine Rem 40X actions are only made in the .308 length, although they have been chambered in longer cartridges up to and including the 300 Win. Mag. Ejecting a loaded round from one of these actions usually requires pulling the bolt.

I think the interior length of the short 700 magazine is 2.835.

Ireload2,

That would make sense as some published figures I see for the 260 Rem is 2.835". What confuses me is I've also seen 3.2" for the the 6.5-284.

Just curious and for my education, where, in the "interior", did you take those measurements from?

If a cartridge is too long for the action the over-all-length (OAL) of the loaded round will not fit the magazine box, however, some actions use a magzine block and once this is removed a longer cartridge will fit.

Secondly, is chamber throat deminsions which a case that is too long will require the bullet be seated deep in the case and thus limit seating depth and bullet weight options.

That would make sense as some published figures I see for the 260 Rem is 2.835". What confuses me is I've also seen 3.2" for the the 6.5-284.[/quote]\
The 260 fits into my short XP100R action (same as model 5 & 7), there is absolutely no room to spare in the magazine, however.).Similarly, while the 284 will cycle through the short 700 action, the bullets must be seated quite deep to fit the magazine. Which is exactly why my 6/284 is built on a standard 700 action.