Quote Originally Posted by mike16 View Post
check to see that those rear sight screw hole have not been drilled so deep they comprimise the structurl strength of the barrel. I have seen holes drilled completely through one side of the barrel and left divets drilled into the rifling across from the holes. Funny thing is how many times the rifle changed hands over a short period of time and yet nobody knew that there was anything wrong with the rifle.
This may not be quite the issue it seems on the surface, gas operated rifles all have holes drilled along various parts of the barrel, and some have divots from over drilling as well, it doesn't seem to heavily degrade accuracy in all circumstances. Now it would be important to ensure there is a gas seal for an unintentional port like a sight base and the pressure would be dictated upon location of the hole or "gas tap". While a hole through the barrel may be undesirable, it doesn't necessarily mean a barrel is suddenly ready to burst.

Proper inspection and profession assessment would be the order of the day if a hole was found to enter the bore.