Hello Hunter 59.

Lets see.
WSM= Winchester Short Magnum.
SAUM= Short Action Ultra Mag.
RUM= Remington Ultra Mag.
Remington Mag.
weatherby mag.
Express= 280 Remington

I hope that I have this correct.

They are all differant as far as too what caseing that they use. Same bullet dia. just differant caseings. They are used for yardages as well.

I personally like the old plane jane 7mm Remington mag. For wha I use it for it works perfectly. (300 yards and less)

If you have to shoot out past 400 yards then you might use a Weatherby, or the Remington Ultra Mag.

I dont like to take those kind of shots myself.
So I stick with my old 7mm Rem.

hope it helps a little. Maybe someone else might get more into detail than I have .
Oh and by the way. I like the Remington rifles. I have never had any trouble with any of them that I have bought.

Good luck.
hunter338