Actually I was thinking of a re-barrel to 24-26" with a 1:16 or 1:18 twist. As far as your theory goes have a look at this site
http://www.gsgroup.co.za/08articles.html
Don't know anything about the company but what he has to say makes perfict sence.
Your getting that out of a rolling block interesting. Your not that far off from the early cordite loads.