180's will work in the RUM, but where you are really going to see it shine is in the heavier bullets. Take a look at the 215 or 230 Berger Hybrids, the 200 Nosler Accubond, or the new 210 Long Range Nosler Accubond.
I've used retumbo exclusively with my 300 rums in one (my sps) I use 180gr sciroccos in the other (my custom) I use the 230gr Bergers. I haven't shot anything with my custom with the 230 Bergers but I've shot a lot with the 180 gr sciroccos and 190 gr Bergers. Both are very impressive! But the 180 gr sciroccos perform amazing on game. The deer didn't do so well with them this year!
My dear boy if 5 miles away they don't sit up in their beds and ask what the HELL was that, the gun is not big enough!