In this guide, we will explain the footprint and mounting of the Sig Sauer Romeo 4XT-Pro red dot so you can be sure it is compatible with your firearm.
Red dots are not made to a particular industry standard, so it is important to know which red dot is compatible with the firearm you want to use it with.
We will cover what to look for on your firearm and the specifics for mounting the Sig Sauer Romeo 4XT-Pro red dot.
Firearm Requirements for Mounting the Sig Sauer Romeo 4XT-Pro
The Sig Sauer Romeo 4XT-Pro red dot was designed to be used on carbines, pistol caliber carbines (PCCs), shotguns, and AR platform pistols. This red dot is a full-size red dot and too large for handguns like the Glock 17, Sig P320, or 1911s.
First, your firearm must have a standard Picatinny rail mounting system. Military spec AR platform uppers have a standard Picatinny rail machined into them. Many tactical type shotguns also have a standard Picatinny rail.
The picture below shows the standard Picatinny rails on an AR rifle and a shotgun.
Mounting The Sig Sauer Romeo 4XT-Pro Red Dot
The Sig Sauer Romeo 4XT-Pro comes with a Picatinny rail mount. This is one of the most common mounting systems for full size red dots. It has a center lug with a stationary rail on one side and a clamp on the other.
In the picture below, you can see the bottom of the optic beside a standard picatinny rail.
This optic comes configured to a standard Mil-spec height of 1.41 inches. This allows the optic to be used in an absolute co-witness configuration with back up iron sights. This means that the backup sights will line up directly with the red dot in the center of the optic.
Also included is an optional riser that moves the optic up to a height of 1.62 inches. This setup allows for a lower 1/3 co-witness. This means that the backup iron sights will line up in the lower 1/3 of the optic window, and not directly in-line with the red dot.
The position on the rail that you mount the optic on your firearm is important. On AR platforms, we recommend mounting it to the rail on the receiver, and not on the handguard. The exact position largely depends on the shooter and the type of firearm. If you are going to use backup iron sights, we recommend mounting the rear iron sight before mounting the optic so the spacing can be evaluated.
To mount this optic, simply loosen the hex nut on the mount, but do not remove it. Then, place it on the firearm, bias it towards the barrel, and then tighten the nut. This optic comes with a wrench for tightening the nut, but we recommend using a torque wrench when tightening it to ensure it is secure. Sig Sauer recommends torquing the nut to 65 in-lb.
Will the Sig Sauer Romeo 4XT-Pro Red Dot Fit your Firearm?
The Sig Sauer Romeo 4XT-Pro will fit any firearm that has a standard Picatinny rail mounting system. All military spec AR platform rifles, carbines, and pistols and most tactical style shotguns have a Picatinny rail. This red dot will not fit on pistols like Glocks and 1911s.