The same idea crossed my mind that whomever drilled that pea sized weep hole half way down the rib hit the barrel. That's the only place I see anything in the barrel. However, the weep hole is large enough that he may have hit the other barrel also. And if the gun was shot with the hole in the left barrel, I'm wondering if the pressure going through the hole may have damaged the other barrel.
I have a small boroscope I use for work and I am going to try to slide it down the barrel tonight or tomorrow to see if I can see the hole.
Pulling the ribs may get expensive and patching a hole in a barrel is no gaurantee. Finding a replacement barrel would be my first choice.
The barrel has no rib extension.
