Guys will the RCBS Partner press work for my 300 ultra? I know there are some better options but i ordered a pile of new gear and am trying to keep cost down a little bit. As always thank you guys for the help.
I've used the partner press on a portable stand to load thousands of 22-250 shells, hundreds of 270 win, 300 win mag, and 300 WSM shells as well as probably two hundred 300 Tejas rounds, with zero problems. To get you up and running you'll be fine with that press till you decide to upgrade.
"..will the RCBS Partner press work for my 300 ultra?"
Will it "work?"; sure. Bigger question is, for how long? That's a small alum alloy press and you would be pushing it's rational strength limits. They commonly have the base snap off due to over stressing when sizing large cases such as your's.
If you want a low cost single stage iron press get a Lee Classic Cast and you'll never need to upgrade at all. It's the best available press of its general type and the price is right too.