I don’t have an AR, but have a Ruger Ranch Rifle. Lots of fun, but not as accurate as an AR. I may put a heavy barrel on it to get accuracy up there.
You need to rebed the stock. That cures a lot of problems with the mini-14.
The trigger can be improved as well.
The standard sights are rather crude.
.303 British.
I have 2 Ranch Rifles and another Mini 30 and all are accurate. The Mini 30 is probably the least, but look at the round. No problem taking deer at 150 yds. The 2 Mini 14’s are VERY accurate. If you are experiencing problems, maybe have a look at a defect in the stock. I have them scoped with 3x9’s( cheap) and they can hit a quarter at 100 yds, certainly no more than a silver dollar with bench rest at 100yds. I’ll bet a gun shop could find something and fix it cheaper than a new bull barrel bought and mounted. The way the action fits in the stock along with the trigger box is critical and I was told not to keep disassembling it by more than a few. I was told back in the Army not to take my M-14 apart very much. It seems to loosen the action in the wood to do that.