Adds in the missing 480px-797px breakpoint range to Bootstrap 3 for SASS

bootstrap-ms.scss

// Bootstrap Mid-Small - col-ms-* - the missing grid set for Bootstrap3.
//
// This is a hack to fill the gap between 480 and 767 pixels - a missing range
// in the bootstrap responsive grid structure.  Use these classes to style pages
// on cellphones when they transition from portrait to landscape.
//
// Contains:
//   Columns, Offsets, Pushes, Pulls for the Mid-Small layout
//   Visibility classes for the Mid-Small layout
//   Redefined visibility classes for the Extra Small layout
//
// See https://github.com/twbs/bootstrap/issues/10203 for more info.
// Original gist: https://gist.github.com/andyl/6360906
//
// Instructions: Add the following to the end of bootstrap.scss
//
//   @import "bootstrap-ms";
//

// Mid-Small breakpoint

$screen-ms: 480px !default;
$screen-ms-min: $screen-ms !default;
$screen-ms-max: ($screen-sm-min - 1) !default;

// Redefined Extra Small max value (Can't override non-default variables in SASS)
$screen-xs-max-new: ($screen-ms-min - 1) !default;

// Common styles (see make-grid-columns() in bootstrap/mixins/_grid-framework.scss)

.col-ms-1,
.col-ms-2,
.col-ms-3,
.col-ms-4,
.col-ms-5,
.col-ms-6,
.col-ms-7,
.col-ms-8,
.col-ms-9,
.col-ms-10,
.col-ms-11,
.col-ms-12 {
  position: relative;
  // Prevent columns from collapsing when empty
  min-height: 1px;
  // Inner gutter via padding
  padding-left:  ($grid-gutter-width / 2);
  padding-right: ($grid-gutter-width / 2);
}

// Misc. class adjustments for col-ms

@media (min-width: $screen-ms) and (max-width: $screen-ms-max) {
  .container {
    max-width: $screen-sm - 20px;
  }
  .hidden-xs {
    display: block !important;
  }
}

// col-ms grid

@media (min-width: $screen-ms-min) and (max-width: $screen-ms-max) {
  @include make-grid(ms);
}

// Visibility utilities

@include responsive-invisibility('.visible-xs, .visible-ms');

.visible-xs-block,
.visible-xs-inline,
.visible-xs-inline-block,
.visible-ms-block,
.visible-ms-inline,
.visible-ms-inline-block {
  display: none !important;
}

@media (max-width: $screen-xs-max-new) {
  @include responsive-visibility('.visible-xs');
}
.visible-xs-block {
  @media (max-width: $screen-xs-max-new) {
    display: block !important;
  }
}
.visible-xs-inline {
  @media (max-width: $screen-xs-max-new) {
    display: inline !important;
  }
}
.visible-xs-inline-block {
  @media (max-width: $screen-xs-max-new) {
    display: inline-block !important;
  }
}

@media (min-width: $screen-ms-min) and (max-width: $screen-ms-max) {
  @include responsive-visibility('.visible-ms');
}
.visible-ms-block {
  @media (min-width: $screen-ms-min) and (max-width: $screen-ms-max) {
    display: block !important;
  }
}
.visible-ms-inline {
  @media (min-width: $screen-ms-min) and (max-width: $screen-ms-max) {
    display: inline !important;
  }
}
.visible-ms-inline-block {
  @media (min-width: $screen-ms-min) and (max-width: $screen-ms-max) {
    display: inline-block !important;
  }
}

@media (max-width: $screen-xs-max-new) {
  @include responsive-invisibility('.hidden-xs');
}

@media (min-width: $screen-ms-min) and (max-width: $screen-ms-max) {
  @include responsive-invisibility('.hidden-ms');
}

Thanks so much, you saved my time!
Anyway I'd not include the max-width on grid media queries since you need to add an extra grid class to maintain the number of column when you surpass 767px and it's against Bootstrap mobile-first approach.
The gist description is also wrong, it 767px and not 797px.

Thanks for this code you made my day ;)

Thanks a lot for this tip!