Is a Remington 700 long ultra mag action different than a standard long action, or is it just in the bolt face?

Bolt Face,Magazine Box and not sure if they screw around with the rails

I made up two .300 Ultras on std. Rem. 700 mag. actions .. The only thing they said needed changed was the magazine box.. I bought that from Rem. during the time the barrels were being fitted..
Sold one to one of my former students.. He loved it and had one made for his dad.. They just put the barrel on the action and didn't change the box.. Seemed to work fine...

so the overall length of the action, thickness of the steel, and the thread pitch are exactly the same as a long action?

Yes, and the bolt face is the same as any belted magnum (.264, 7mm Rem, .300 Win, etc.).

Are the feed rails any different? Everything else on my LA mags and ultra mags measure the same other than the ultra box has the cutouts.

Bb

They are the same from what Rem. told me except the mag. box.. And as I mentioned one of my pals built one with the std. mag. box with no problems...

I put a 300 UM together on a regular magnum action, and had to open up the front half of the feed rails a hair, as the loaded rounds wouldn't release soon enough from the mag, and bind up.

I had a UM action to measure and compare, so I just did a little filing to make it work. Wasn't much, and it was S/S, so no biggie.

There a are a ton of misconceptions out there regarding Rem 700 actions, more specifically the differences, and lack of differences between actions factory chambered for various cartridges.

While the previous posts have satisfied the OP's questions I'd like to add what I've found from 20 years of tearing down, rebarreling and shooting 700's, probably over 100 rifles torn down and reassembled and rebarreled probably 25 or 30 of them.

I've had RUM's in 7mm, 300 and 338 go thru my hands. They all would feed 7mm Rem Mags and 300 Win Mags without a hitch.
RUM cases will feed out of the mag from a factory chambered 7mm Rem Mag or 300 Win Mag. You will only get two down in the box though because of the lack of cutouts in the walls of the mag.
The followers might be different but it isn't by much and appears to have little effect when swapping cartridge types.

A few other incorrect statements you will hear about 700's.
"The 6.5 x 55 Swede has a bigger bolt face"....untrue, 700's has more than enough clearance in the bolt face to accept the slightly larger base of the 6.5SE....and lots of North American made 6.5 cases have the same rim as a 270 or 30-06.

"You need a magnum length 700 for a magnum cartridge"
ALL long action 700's have the same length mag box whether it left the factory as a 257 Roberts or a 375 H&H....the only significant difference is the bolt face.

"You can't rebarrel a "magnum" action to a standard cartridge"
I put together my first 35 Whelen on a 7 Mag action just by swapping the bolt as I had an extra 30-06 bolt. It fed perfectly.
I couldn't measure any significant difference between the feed rails of a factory 7 Mag and a 30-06 receiver.

The above applies to long actions only.
The long action 700 has to be the most forgiving action made in regards to feeding various cartridges.

rembo, I seen your old post regarding the 700 long action utilization for a 300 RUM. I own several RUM rifles and I love using them. I know they are old news now but I still love to shoot them. I purchase all of mine built but getting ready to build a 375 RUM Left Hand. I have a couple of new 700 L/H Long Actions actions and was planning on using one for the 375 RUM. I am going to have Shaw barrel in for me. I am planning on a stock from Stocky Stocks and the Waytts Bottom Metal and magazines.

your post was helpful in knowing that the action will work fine. Not sure you will even see this as I am replying to a very old post.