I'm buying these 25" long drill bits from harbor freight:
http://www.harborfreight.com/25-long-wood-bit-set-18-316-14-3-piece-68822.html
Will add brass bushings around them to guide them. Washers welded to the drill bit will keep the bushings in place.
I also bought this el cheapo borescope which should fit in a 308. Largest diameter is .29″. May require some sanding.
http://bpcr1885.net/34-borescope/
I think I'll be good from here on out.
Do NOT do any welding on the drill bits. all you'll end up doing is destroying the bits outright or weakening them to the point that they'll bend/twist/break under use.
Get a brass tube/sleeve to slide over the drill bit that will fit the bore. This will protect it from contact with the bit. Preferably one that just fits the bore and is just big enough for the drill bit to fit through.
Before you start, get a brass rod the same diameter as the bore and grind one end to a point, with the point centered. Use this as a center punch to dimple the bullet in the barrel to provide a starting point for your drill bit.
Then drill a little bit, stop, pull everything out, and flush the particulate out of the barrel. Clean the bit point and drill a little bit more. Repeat frequently until you've drilled through the obstructions.
Then use a brass rod the same diameter as the bore to slide down the bore and tap out the rest of the slugs.
This will get the bullets out...but you will still need to clean the bejeebers out of the barrel to remove all traces of lead/copper. Then get it inspected.
If I were you, however, I would simply consider retiring this barrel. Life is full of wonders and we have short enough lives to experience these wonders as it is. It's not worth it to even consider using a suspect barrel.