Installing Novak’s sights on a Colt 380 Government (Mustang)

Introduced in 1983, the Colt Mark IV Series 80 Government Model is a compact .380 ACP caliber pistol that looks similar to the 1911. Originally manufactured from 1983 to 1996, it was recently reintroduced on alloy and polymer frame versions. In this post, we’ll install a set of Novak’s sights on an original production gun.

From the factory, the Colt 380 Government has a rear sight in a dovetail and a front sight that is formed as part of the slide. To install Novak’s sights, new dovetails need to be cut on the front and rear of the slide.

Before we get to work, please read the following disclaimer:

The contents of are produced for informational purposes only and should be performed by competent gunsmiths only. and its authors do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.

Any modifications made to a firearm should be made by a licensed gunsmith. Failure to do so may void warranties and result in an unsafe firearm and may cause injury or death.

Modifications to a firearm may result in personal injury or death, cause the firearm to not function properly, or malfunction, and cause the firearm to become unsafe.

For this project, I ordered the following from Brownells:

Both of the sights fit a 65 degree x .330″ dovetail. The front sight requires a cut that is .060″ deep, while the rear sight requires a cut that is .062″ deep. To make these cuts, I ordered a Cryo-treated 65 degree x .330 dovetail cutter from Brownells.

A project like this requires access to a milling machine. While I assume that it would be possible to file out a dovetail, most people that would have the skill set necessary to pull this off and have it look good, would likely have a mill. So if you don’t have one, it’s probably a job for a professional gunsmith.

We’ll begin work with the front sight. Notice that the factory front sight is milled into the slide. Also note the radius at the top of the slide. Care must be take to remove this sight and not damage the slide’s profile.

Before I get to work, I always like to measure the parts I am working with. A long time ago I learned not to take standard measurements for granted. In this image, I am showing my notes for the front sight. I need to cut a 65 degree dovetail that is .330″ wide with a depth of .060″. Based on my calculations above, I determined the center line of the dovetail needs to be at least .336″ from the front edge of the slide. Since the front edge of the slide also had a slight radius, I added .014″ and decided I would machine the dovetail at .350″ from the front edge.

Before I began working on the slide, I wrapped the sides in masking tape to protect the finish. Next, I squared the vise on my milling machine and set the slide on a pair of parallels. I used a 3/8″ end mill to machine off the front sight.

With the factory front sight removed, I was able to begin work on the dovetail. I used an edge finder to locate the front edge of the slide, moved the x-axis over .350″ and set a 3/16″ four-flute carbide end mill to cut a pass .055″ deep. This pass hogs out most of the material and helps prevent the small dovetail cutter from breaking.

Next, I place the .330×65 degree dovetail cutter in the milling machine. I have this set to cut .060″ deep. I make a very slow deliberate pass. Breaking a dovetail cutter midway through a cut presents a difficult set of challenges. Trying to pick up the exact location of the cut with a new tool can be quite daunting.

With the front dovetail cut, I can begin work on the rear dovetail. Similar to the full size 1911 Novak’s cuts, the cuts on the 380 Government requires a flat cut to remove the factory dovetail. I use a 4-flute 3/8 carbide end mill for this. Rather than drift the rear sight out and risk damage to the slide, I prefer to simply cut it out. Note, on the Colt 380 Government, the rear sight retains the spring for the firing pin block. This should be removed and preserved once you take off the rear sight.

Once the factory’s dovetail is machined away, I use the 3/16″ end mill to cut a relief groove for the dovetail. The centerline of this cut is .725″ from the rear edge of flat cut that I just machined. I made the relief cut .055″ deep, similar to the front relief cut.

With the same .330×65 degree dovetail cutter, I make a .062″ deep cut (when measured from the flat surface I just machined) centered .725″ from the rear edge of the slide.

The front and rear sights can now be fit. I hold the slide in a set of bronze vise jaws to prevent damage while I work. I like to use a 65 degree safe edge file and some stones for this.

I also like to use a piece of nylon to drift the sights into place. I find this prevents damage to the slide or the sight.

I really like the look of Novak’s sights on this gun!

Viola! This is how Colt should have shipped the guns in the first place.

If you need Novak’s sights installed on your Colt Mark IV Series 80 Government Model or Mustang and your local smith can’t do it, you can contact me at 782 Custom Gunworks LTD.