One should not attempt to use a pressure cooker without the book "Great
Vegetarian Cooking Under Pressure" by Lorna Sass. She gives all the right
proportions and cooking times, and her recipes are vlf and delicious!
So, for brown rice, first of all, never cook it directly in the pressure
cooker. I use a small casserole dish that I place inside the cooker, into
which I put 1 part long-grain rice to 2 1/4 or so parts water, or 1 part
short-grain rice to 3 parts water. There should be at least 1 inch of water
in the pressure cooker before the casserole dish goes in, but not so much
that it'll spill over into the casserole. I cook it about 5 min on high and
let the pressure come down naturally for another 10-15 min. If the rice
isn't done by that time, simply replace the lid and bring the pressure up
again, but not for as long.