Barrel length has little to do with bullets stabilizing. It may make you more stable while aiming. Matching the bullet weight/length to the correct rate of twist is the main factor. My Savage uses a 24" with a 1-24 twist yet the fps is very close to longer barrels using BH209. Their OAL though is pretty long due to the action length and they are heavy.

I shoot 385-400gr bullets in sabots out of my GMB54 without any issues...besides a lot of recoil