Annealed copper 3/16 is only rated at around 1600 -- 1900 psi working pressure. There is a REASON that NO manufacturer uses copper tube in brake systems
exactly, brakes work at a working pressure of about 1200 PSI under easy braking, that would be if your coming to a stop sign you know is there and have plenty of time to stop.
the trouble starts when you have to stop quick with no notice such as an animal jumps out in front of you or a kid comes out in front of you on a bicycle or chasing a ball
then the working pressure can be as high as 2500 PSI+ your copper lines are blown and your doing your best not to be front page news the next morning
good steel lines with no rust is the way to go, and inspected often, its the only thing that stands between a nice cruise and jail time