If you use something like this then you don't need the copper caps:
http://www.ebay.com/itm/PARKER-3GF-10-Seal-Bonnet-45-deg-Copper-Flare-PK-10-/381935277769?epid=11107...
http://www.ebay.com/itm/PARKER-3GF-10-Seal-Bonnet-45-deg-Copper-Flare-PK-10-/381935277769?epid=11107...