I wouldn't have thought a 12 twist would make it happen at levels under 4000 ft. There's the example. My buddy's cannot stabilize the 69 SMKs at 1000' elevation. Hitting paper sideways at 100 yards. Every gun is different.My 12 twist 22-250 shoots 69 SMK's accurately @ 3615 from a 26" barrel. I did my initial load development at roughly 1000 ft asl and 70 degree temps. Sierra 69 TMK's and Hornady 68 BTHP's would not stabilize.
To the OP, go ahead and shoot up the Winchester White Box rounds you were given. As others have said, you will have some pretty good brass for reloading after you are done.
IMO, the 53 VMAX is without peer among .224 varmint bullets. Load them atop RL-17 or IMR8208 for speed AND accuracy.