I have bumped into several articles in the past year mentioning this wildcat..it was even mentioned in Noslers new reloading manual in the info on the 338 Ultra-mag..

Not sure how much more it can really do than the .416 Rem I currently have...but interesting to read the articles by those who have a rifle chambered to this round. Per the information I have read it seems it is very similar to the 416 Dakota..

Here is a an Alaskan hunters post from another website who apparently has one:

If you do your own loading, the wildcat 416 Remington Ultra Mag is a great round. It outperforms all the 416's exept the 416 WBY Mag. It fits any long action, and is an easy neck up from 375 RUM brass. I got my dies from Redding. My rifle is a Winchester 70 that was originally chambered in 300 RUM. It has a 22" Lilja #6 barrel. I am getting a measured velocity of 2550 FPS with 400gr Barnes Triple Shocks using RL 15 powder. This is not a maxed out load at all, and very reliable, shooting about .75" - 1.00" consistantly at 100 yards. Kevin Weaver of Weaver Rifles out of Peyton CO built the rifle. I have the twin to this rifle chambered in 375 RUM (with a #3 Lilja) shooting 300gr Noslers at 2800 FPS that is a lot more unconfortable to shoot. Anyways if you are a 416 fan, the 416 RUM is a great round to think about, something differant that not everybody has.

I have not taken a brown bear or moose with it yet, but it has plenty of horsepower to get the job done on either animal, hopefully in 2012 I will be uisng it on the pennisula for brown bears. That is the next season I can hunt due to the one bear every four year management area.

I find this very interesting as I have and have used the 300, 338 and 375 RUM's ..all with excellets results and all very accurate..the performance on elk size game is devastating...

Ripp