Barrel Index, Need Help

[browningautorifle]

a machinist bubble level

No, you need an angle meter. This will allow correct adjustment, the bubble is too subject to interpretation. This is a cheap enough tool to allow you to read exactly how many degrees out you are. Use the front sight base with the front sight removed and the flat behind the rear sight on the receiver. Here's the one I have.

I did have an occasion to have a bent barrel. It was bent so far back you wouldn't have believed it. It was bent since the factory...it had to be...and couldn't be zeroed with all the indexing in the world.