Nice post above me...lol.
Anyway, I posted about the carb capacity of standard beer bottles not too long ago. General concensus was around 4. It was mentioned that 22oz bombers were probably a little stronger though.
If you want to be safe, I would go with belgian or champagne bottles at that high of carb. If not, at least put them in a sealed rubbermaid for the carb process.
Since it sounds like you will be beer gun filling, I think that is slightly less hard on the bottle, though it will still be close to capacity.