My next centerfire rifle….may well depend on what shows up on the auction site I frequent
Nonetheless a .300 RUM of some kind is on the short list.
As for old rifles that I'm always keeping my eyes open for:
Of particular desirability to me would be an old Savage 99 in good condition chambered in .250-3000 savage or .358 Winchester. To a lesser extent the .300 savage as well, but the 250 and the 358 models Just have such a cool factor to me, I do hope to obtain them before I die. We never know when our time is up. I'm turning 32 in a few weeks, Lord willing I've got some time haha.
And in the intermediate future, not for a few years but not decades down the road either: my first build, will be based on a 32 inch bartlein .257" barrel I got for pretty cheap very lightly used. It's in 25-06 ai at present. I'm going full hot rod just cuz I've never done that before. Either a .25-300 weatherby, .257 stw, or .25-300 RUM. Leaning most strongly to the .25-300 weatherby (and PETERSON makes 6.5-300 wby brass being one of the big reasons why). I already have a 24 inch barreled .257 weatherby. A 32 inch 25-300 weatherby ought to go FAAAAAST!!!!
Sorry, couldn't pull from any of the list above. 270 win #1, 35 whelan #2. These 2 rounds represent 55 years of hunting. The whelan coming later when remington introduced it as a factory round.