Occasionally you may encounter the need to cut and crown a pistol barrel. While this can be accomplished with certain hand tools, use of a lathe makes the process easier. In this post, let’s look at how we’d do just that.
Unfortunately, the owner of this pistol lives in an Anti-2A state and isn’t allowed to have a threaded barrel on his recently purchased CZ75. He had it shipped to us and we cut the threads off and crowned the muzzle. While you might not ever want to remove threads from a pistol barrel, you may want to freshen up a crown or blend it closer to the slide. The methods shown here could be adopted for such use.
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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.
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For this project, I ordered the following items from Brownells:
Here is our pistol barrel before. The threads have to go. Since parts of the barrel have a slight taper and the rear of the barrel has the chamber and locking lug, our lathe won’t grab the barrel very well with a standard chuck. We’ll need to make a fixture.
I like to keep some round aluminum stock around the shop for situations like this. The aluminum cuts easily and doesn’t mar most firearm surfaces. I cut off a piece of 1″ round stock around two inches long, chuck it in my lathe and face it off.
The lathe we use is a Precision Matthews PM-1440GT gear head lathe. We’ve found the PM-1440GT to be an excellent lathe.
I take a few minutes to measure the outside diameter of the barrel and find a drill bit that’ll fit. In this case we measured the barrel at .503″, so a 1/2″ drill bit would work just fine.
I head back to the lathe and drill a hole through the center of the fixture block. I start with a #3 60-degree center drill (not shown) and follow up with my 1/2″ drill bit.
I grab the barrel and see how close it fits to the hole. I got lucky! This is why you use reamers to hold specific diameters folks! The 1/2″ drill bit opened up the hole just enough over sized that the barrel fits through. This means I don’t have to use a boring bar to open it up.
The block is removed and secured in a Multi-Vise. I drill and tap it for a cross screw. Since we only work on guns, that ended up being a 1/4-28 (M700 action screw size). That is mostly because we only have gun screws laying around. Course threads on a standard UNC thread would have been a better choice if we had the screws on hand.
At this point I can grab the barrel in the fixture and clamp it in place with the screw. A few quick notes, a brass tip to prevent damage would be ideal on the end of the screw. Since I don’t think I’ll be cutting off many CZ-75 pistols in my shop, I didn’t think the machine time was worth it. Instead, I took a big aluminum chip and placed that between the tip of the screw and the barrel. Also, while it isn’t shown this way in the picture, you want to have the screw aligned with the locking lug on the end of the barrel. This way they won’t get in the way of the jaw.
I head back to the lathe and dial in the barrel. I am using a set-true chuck. Even though it only has three jaws, it is on a plate that can be adjusted in the same fashion as a four-jaw chuck.
The barrel is now ready to go!
My first operation was facing the barrel to the proper length. For this op I had my scribed line flush with the fixture. I simply faced the barrel to the proper length.
Next, I used a boring bar to cut a slight crown by withdrawing my lathe’s compound.
All done! It looks good, but I can’t help feeling bad that I had to cut the threads off!
I always like to hit the surfaces I machine and polish with a little bit of cold blue when I am done. The CZ barrel steel worked exceptionally well with the Brownells 44/40!
A look at the finished barrel and the fixture I made to cut it.