Machining front cocking serrations on a Glock slide

Front cocking serrations are popular with some pistol shooters. Once the hallmark of custom 1911 builders, these cuts were quickly adopted to production 1911 pistols, and then to other production guns. They have become so prevalent on factory pistols, that some custom 1911 makers have actually stopped adding them to slide to give the gun a custom look.

A few years ago, shooters started adding cocking serrations to the front of their Glocks. When I installed an RMR on my Glock 22 (Milling a Glock slide for a Trijicon RMR) I started to see the benefit. The addition of an optic changes the handling characteristics of a pistol because I could no longer grab the top of the slide the way I used to.

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If you want to match the factory cuts on your slide, you’ll have to embrace the metric system. The grooves on a factory Glock slide are 3mm wide- that means to match them, you’ll need to invest in some solid carbide 3mm end mills as well as a 3mm collet or end mill holder.

I ordered the following items from Brownells to complete this project:

Before you start cutting you need to spend time planning. The factory serrations I measured on my Glock 22 were 3mm wide (.120″), .025″ deep, with .070″ in between each groove. There are seven grooves total. On my pistol, a well used police department trade-in, I decided to match the number and spacing of the front serrations I’d be cutting with the factory rear slide serrations.

Locating the new serrations took some time. If you do a Google image search, you’ll see scores of designs. Many of these designs use the cuts to frame the markings on the left side of the slide. While these look nice, I decided to locate my cuts where I would use them. After careful deliberation, I decided to cut the last groove in line with the end of the accessory groove on the frame. The frame is narrow for the accessory rail and becomes wider at this point.

On the left side of the pistol, “Fulton County Ga. Police” was engraved by the previous owners. I decided to cut through this marking. The engraving was too deep to sand off, so I left the remaining text as a conversation piece.

I planned my slide cuts from the rear of the slide towards the front. Since I wanted the last cut to line up with the end of the frame’s accessory rail, I measure to that point on the slide. On my pistol it was 2.000″. I subtracted half of the width of a 3mm groove (.120″/2=.060″) and subtracted that value from 2.000″, 2.000″-.060= 1.940″. 1.940″ from the front of the pistol would be the centerline of the last cut. From this point, I subtracted the sum of diameter of the groove (.120″) and the width of the space in between each groove (.070″) from the location of the last cut (.120+.070=.190″). 1.940″-.190″= 1.750, this would be location of the centerline of the second to last cut. I repeated the calculation until I determined the centerline of all seven cuts I would need to make. The centerline of the cuts would be made at .800″, .990″, 1.180″, 1.370″, 1.560″, 1.750″, and 1.940″ from the front edge of the slide.

I made each one of the cuts in one pass on the mill. A sharp solid carbide 4-flute 3mm end mill was used to cut through the slide.

The completed serrations on the right side of the slide (above).

The left side of the slide presented a bit of the problem. At the locations of the grooves, the slide was roll marked with the Glock logo, “22” and “Austria”. I consulted Rifleshooter.com’s legal team and was told I could remove these markings, however, I decided to see if I could cut around them. Since the Glock logo was bigger than “22” and “Austria”, I decided to stop the cuts at different points on the slide.

To make the stopped cuts I zeroed my DRO at the bottom of the slide. On the first groove cut, I stopped the cut once the DRO read .065″ (keep in mind the cutter is .130″ in diameter, so the cut is actually .125″ in from the base of the slide). I came around the other side from the top, and cut until the DRO read .635″. The second and fifth lines didn’t run into the text, so they didn’t require stop cuts. The third, fourth, sixth and seventh lines, required stop cuts, however, since the text was smaller, I cut in further. On these lines I stopped the cut from the bottom of the slide when the DRO read .190″, and from the top, when the DRO read .510″.

In the photo above, you can see the first and second cocking grooves I cut on the left side of the slide. Note the proximity of the Glock logo to grooves.

Taking the time to measure and plan paid off.

The completed cuts on the left side of the slide (above).

Since the side looked so good, I decided to continue to the top. I noticed when I pinched the top of the slide, my thumb would rest against it. Trying to match my hand placement, I decided to make the first set of grooves .423″ in from each side. This value would then decrease .030″ on each successive groove. The centerline of each groove would be at the same location as the side cocking serrations from the front of the slide. I cut one side, and then the other. My DRO readings for each successive cut were (left side/ right side, the DRO is zeroed off the left side and the slide is 1.005″ wide) .362″/.643″, .332″/.673″, .302″/.703″, .272″/.733″, .242″/.763″, .212″/.793″, and .182″/.823″.