So I looked through the myriad of thoughts and if this is a duplicate, apology up front. Don't think I saw it.
One of the reasons I bought a RUM early in my LR hunting life back in 2001 was its speed. This was when exposed turrets and "clicking" was a bit harder to find and DOPE was all on paper. How fast things have changed. 404 Jeffrey is the parent case (543 bolt face) for many new magnum cartridges and is for the RUM.
I continued to run it until about 2013 when I built a 30 Nosler out of it. Reason, efficiency with the larger/longer ELR bullets. More space in the mag to run the longer bullets out of the case, reducing pressures and allowing me to load the case more full, while giving me the ability to add freebore to the chamber and control jump. Will the RUM run them, absolutely, but inherently the Nosler will run them more efficiently, no doubt.
With that, I have experience with 28N as well. If you have enough shank on your rifle, it is likely you can set it back 1/3 to 1/2 inch and re-chamber in 28N without an issue and possibly have a bit more barrel life due to the new chamber. RUMs are notorious for wearing out the first inch of a barrel. I am actually doing this right now with my current 300 RUM that has a 3 inch shank. I am setting it back and making it another 30N.
I am a big fan of both the 28 and 30N and I think they are a sweet spot for 30 cal ELR and speed that can combine the advantages of hand loading while giving the shooter OTC ammo options.
Really you can use any .543 bolt face cartridge so my 2 cents - rechamber in 28N if you have enough shank.