Cutting & Crowning a Barrel with Hand Tools
June 23, 2016
Some of us are tinkerers at heart and enjoy working on our guns. It's interesting and educational and leaves us with a sense of pride. Another benefit is saving money that you would have to pay a gunsmith.
Some tinkering projects are simple enough that no special tools are required. Other projects require special tools, and they might cost more than what a gunsmith would charge for your project. I've bought a few specialized tools over the years and have used them on several projects, so I've saved money in the long run. But if your project is a one-time-thing, you have to decide which is the best course of action.
I'm a fan of the .38 Super cartridge. It's very versatile and I have several 1911 pistols chambered for it. Having a .38 Super in a different platform adds variety to life. A Glock is about as different as you can get from a 1911, so why not a .38 Super Glock?
Glock does not make a gun in .38 Super, but Lone Wolf makes a .38 Super conversion barrel for Glock 10mm pistols. I bought one for my Glock 20SF. The Lone Wolf barrel is 6 inches long, a tad longer than the Model 20's 4.6-inch barrel. Lone Wolf can cut it to the desired length for a reasonable fee, but I wanted to test the velocity from the 6-inch barrel before I cut it down to 4.6 inches. Plus, I had all the required tools from other barrels I'd cut down, so there was no reason I couldn't do it myself.
Shortening a pistol barrel is not difficult and can be done with hand tools, but it requires special tools to do it correctly. You can't just whack it off with a hacksaw and leave it at that. Well, I guess you could, but accuracy, as well as aesthetics, would be horrible.
The end of the barrel has to be squared, so when the bullet leaves the barrel, it does so at the exact same moment at every point of the bore's circumference. If the barrel is not squared off, and the bullet exits the barrel on, for example, the right side, before it does on the left side, the asymmetrical gas escape can cause the bullet to yaw, and accuracy will be poor.
Squaring the barrel requires specialized tools: a facing cutter, a crowning cutter and caliber-specific pilot. The pilot keeps the cutter aligned with the bore axis so that your cut will, in fact, be square with the barrel. I used Brownells' brand tools. They sell them individually or as a kit. Other companies make tools for this purpose, such as Pacific Tool and Gauge, Manson and Clymer. You can even rent the tools from 4D Reamer Rentals. The other tools required are a vise, file and sandpaper.
The factory Glock 10mm barrel protrudes about 1/8" from the slide, and my intent was to cut the .38 Super barrel to more-or-less the same length. You can cut your barrel to whatever length you desire, to extend a little, match the factory barrel length or to be flush (or below flush) with the slide. It depends on what look you're going for, or purpose you have in mind.
I installed the barrel in the slide and marked it with a magic marker. My cut was just a little past this mark, since I knew it would have to be squared, which will remove a little length depending on how square I made the initial cut with the hacksaw. I wasn't especially concerned about the final length, and if it was a little longer or shorter than the factory barrel, it didn't matter. But if it does matter to you, pay close attention to the length. Having a little extra material at the end that must be removed is better than having it too short.
Be sure to place the barrel deep into the vise so the upper surface of the barrel is below the upper surface of the vise (see the figure). That way you won't run the risk of scratching the 'good' part of the barrel if the hacksaw slips.
I used a hacksaw to cut the barrel. Brownells said a lathe or saw is preferred, but you can use a grinder or cutting wheel if you take it slow and don't raise the barrel's temperature too much.
Once the barrel is cut off, do some initial cleanup and squaring with a file. I like to mark the end of the barrel with a magic marker so I can watch progress and make sure that filing is more-or-less even or removing metal from specifically where desired. Here again, clamp the barrel in the vise with only a small portion of it protruding to protect it from errant file strokes.
Now you can start squaring the end with the facing cutter. Apply lots of oil to the surface being cut when facing or crowning to float away the shavings so they don't scratch the inside of the barrel. Remember, the pilot contacts the lands of the bore, not the grooves. Small metal shards can slip down into the gap between the pilot and the grooves, and oil will help prevent them getting snagged and dragged by the pilot.
After squaring the end of the barrel with the facing reamer, there might be "chatter" marks, grooves, lines or other cosmetic imperfections. These are removed by sanding. Start with a medium grit sandpaper, then work your way to finer grits until you get the desired smoothness / polish. I started with 320 grit paper and ended with a light polish with 1500 grit. I wasn't going for something shiny but wanted to remove any obvious scratch marks from the coarser sandpaper.
Don't use your finger to support the sandpaper since this results in uneven sanding and rounded edges where you might not want them rounded. Back the sandpaper with something firm so it stays flat. A small block of wood is perfect. The barrel's outer edge was rounded with 600 grit paper.
Crowning was the last step. The crown is the very end of the bore, and this is the portion that must be perfectly square to ensure the bullet's symmetrical escape. One could leave the crown as-is after using the facing cutter. After all, the end of the bore is square at that point. But the crown is vulnerable to damage in this state if it is bumped against something hard. Dings and dents in the crown will degrade accuracy, so the crown is usually 'protected' by recessing it by some means.
I used a traditional 45-degree cutter for this barrel, but there are other options available; recessed, 11-degree and round. You can combine different crowns to your liking - for example, a 11-degree followed by a 45-degree. Whatever your heart desires. Once again, make sure you use plenty of oil to float away the cuttings.
After I was done, the barrel measured 4.607 inches long, which is pretty darn close to the Glock 10mm barrel's length of 4.606 inches. Good enough!
There you go. Cut, squared and crowned, all with hand tools. You can do it, too.