Bootstrap col Spacing

i have 3 col grid using bootstrap. I want to make 15px gap in between the col.. max width of the row is 1600px

each col should be w 522 h 476 at 1600px row size..

<div class="row">
  <div class="col-lg-4"></div>
  <div class="col-lg-4"></div>
  <div class="col-lg-4"></div>
</div>

you can edit these spaces in bootstrap less file and recompile it. Right in variables.less

//== Grid system
//
//## Define your custom responsive grid.

//** Number of columns in the grid.
@grid-columns:              12;
//** Padding between columns. Gets divided in half for the left and right.
@grid-gutter-width:         30px;

makes in css:

.col-xs-1, .col-sm-1, .col-md-1, .col-lg-1, 
.col-xs-2, .col-sm-2, .col-md-2, .col-lg-2,
.col-xs-3, .col-sm-3, .col-md-3, .col-lg-3,
.col-xs-4, .col-sm-4, .col-md-4, .col-lg-4,
.col-xs-5, .col-sm-5, .col-md-5, .col-lg-5,
.col-xs-6, .col-sm-6, .col-md-6, .col-lg-6,
.col-xs-7, .col-sm-7, .col-md-7, .col-lg-7,
.col-xs-8, .col-sm-8, .col-md-8, .col-lg-8,
.col-xs-9, .col-sm-9, .col-md-9, .col-lg-9,
.col-xs-10, .col-sm-10, .col-md-10, .col-lg-10,
.col-xs-11, .col-sm-11, .col-md-11, .col-lg-11,
.col-xs-12, .col-sm-12, .col-md-12, .col-lg-12 {
    position: relative;
    min-height: 1px;
    padding-left: 15px;
    padding-right: 15px;
}