Get some ammo that has a KNOWN reputation for being good and reliable. Take the optic off and then use the iron sights. If it is still all over then you know the issue is more than likely the barrel.
Nothing is foolproof or 100%. You could have a 2K scope and it could be ****ed. You could have a 1500 carbine and it's shooting screwy.
Try to eliminate the issue by removing the variables.

