you could turn it down, but that's when the agony will begin! The barrel is probably going to twist all over the place, and will need a serious amount of straitening. If it's a precision of good quality; it might be worth the trouble.
gary
Several years ago I bought several 1" diameter .224 blanks. A couple were 22" long and the other was 34". Turning down a barrel for a AR isn't hard, just time consuming. I didn't turn any of them down past 3/4" (muzzle end). Now, when I need one, I buy them pre-contoured and do the threading, chambering & crowning and mill the gas port. They arrive where you've got to "fine tune" the shoulder for the gas block.