Yep I have a lefty. It turns whitetails into purple mush at 250 yards with a 180Gr sirocco bonded. It produces energy at 400 yards roughly equivalent to a 30-06 at the muzzle.
I sat down and benched 2 boxes of ammo years ago with the brake on and an additional recoil pad. It didn't bruise me or make me sore at the time but the next day I was having chest pains. I went to the doctor at my wifes insistence not even thinking about the previous days entertainment. They ran a bunch of very expensive tests including x rays. The x rays came back showing I had separated my ribs from my sternum. Yep wont be benching any more than necessary to check zero after that one. The rifle has been in the back of my safe for several years now but I do have some managed recoil and some carefully reduced hand loads using data from one of the ballisticians at Ramshot powders. The .300RUM is a beast plain and simple. Due to game animals blown to smithereens by the original loading Remington now produces ammo in 3 power levels. A full loading for really big game (t rex and such). A loading equal to the .300 win mag for elk sized creatures and a loading equal to the 30-06 for deer.
On the plus side it will reach way way out there with authority. and mine is plenty accurate. Also just FYI the older USA made Burris 4.5-14 fullfield 2 I've had on it since new has a ballistic plex reticle that matches up almost perfectly to the trajectory of the 180gr load to 600 yards just range point and shoot.
It's a well made rifle just like my other 116s, just in a beast of a caliber that I haven't fired in years.

If the one you're looking at is an original .300RUM and not a rebarreled standard long action, they are highly desirable to those wanting to do a .338 edge build because the extra long mag cutout that is on this model will let it function as a repeater, unlike a standard long or magnum action.