Don’t have a MSR (Modern Sporting Rifle), but would like to get one?

Intimidated by all the terminology?

Stay tuned for a series of posts explaining simple MSR terms and functionality.

Today’s terms – “Flat-Top”, “Optics-Ready (OR)”, “Back-Up Sight (BUS)”, “A2 Front Sight”

A “Flat-Top” MSR is one with no pre-installed front or rear sights. The user has maximum flexibility configuring the sights/optics. Flat-tops may also be marketed as “optics-Ready”.

On occasion, the term “optics-ready” has also been used to market MSRs having an “A2” style front sight, but no rear sight. The “A2” style front sight is integrally attached to the barrel and is not easily removed.

MSRs may also come with flip-up front and/or rear sights. Flip-up sights are generally referred to as Back-Up Sights, or BUS. Back-up sights manufactured by Magpul are referred to as MBUS, for Magpul Back-Up Sight.

Image “1” shows the location and appearance of an “A2” style front sight, and a rear sight which is integrated into the removable carry handle.

Image “2” shows the A2 front sight, but no rear sight. This combination is sometimes referred to as “Optics Ready”.

Image “3” shows the same configuration as image 2, but with a flip-up style back-up sight.

Image “4” shows a flat-top style MSR. Flat-tops have no integrated front sight, and no back-up sight. However, this particular MSR offers an integrated mount for installing a back-up front sight.

With few exceptions, most MSRs have a rail onto which either a carry handle or other accessory, including back-up rear sights, may be mounted. This rail is located directly above the charging handle. Some MSRs include an integrated A2 front sight. Other MSRs include a small rail segment in place of the A2 sight, which may be used to mount a flip-up style front sight.

That’s it! Another handful of intimidating terms explained!