Right you are Tom. Could possibly start as low as 360g. And I wouldn't venture anymore than 70grains, of any powder

The Bull Shop: http://bullshop.gunloads.com/ or No Excuses: line of conicals would be a good place to start, and would have to slug the bore and get the actual barrel diameter measurement.

Off the shelf bullets that might work are the 300g Platinum PowerBelt, And you could pay the big money for this bullet, and have it shipped to ya from PRBullet.com: Ultimate 1 QT .45 Polymer Tip - 360 grain