Mossberg 590 Choke Installation

Mossberg 590 choke tube installation final

Mossberg 500/590 Choke Installation

I’m a big fan of installing choke tube systems on shorter-barreled shotguns. Adding one offers increased versatility. Your shorty isn’t simply relegated to a home defense role in the closet, now you can take it to a shotgun steel match and reach those far plates with authority or use it for a turkey hunt in a pinch (depending on the sights you are running).

Most of the 18″ and 20″ barrels on the market do not come with a removable choke. Conversion requires machine work from a gunsmith. In this post I am going to install an interchangeable choke tube system in a 12-gauge Mossberg 590A1. The process here is similar to that used on other shotguns, however it should be noted that many Mossberg 500s have a very thin barrel wall, and the type of choke tube system you install should be selected with this in mind.

Before a shotgun barrel is machined for an interchangeable choke tube system, the barrel needs to be assessed to determine whether or not it is a good candidate for the conversion. For more information on how to do that, see Choke Tube Installation.

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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.

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.

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

I’ll be installing a Rem Choke style system on a Mossberg, don’t worry, it’ll be fine. I like the Rem Choke system because the tubes are fairly inexpensive and relatively easy to find.

I’m embarrassed to say that once, a very long time ago, I tried (and succeeded) installing a choke tube system without a lathe, turning the reamer by hand. While it worked, let me assure you it was a risky thing to do. That was a couple of lathe’s ago and now I am using my Precision Matthews PM-1440GT to do the work.

One of the trickier parts of installing a choke tube is using the lathe to drive the barrel (or reamer). There are a bunch of different ways to set it up (many of which have been captured on this site). However, for something as easy as this plain Mossberg 590 barrel, it can simply be held in the lathe’s 3-jaw chuck. It is important that the surfaces of the barrel that touch the lathe jaws be coated in tape prior to holding them. Failure to do so can result in surface damage.

Since I am driving the barrel in the lathe, the reamer can now be held in a chuck in the tailstock. Note the bronze guide bushing on the end of the reamer. These are available in .001″ increments and retained by an “e” clip on the end of the tool. If the barrel has a fixed choke from the factory, the choke may need to be cut out in order for the reamer bushing to pass into the bore. This isn’t the case on the Mossberg barrel.

I use a very low spindle speed and slowly feed the reamer into the barrel. This will form the barrel to receive the choke tubes. Note that the barrel lug is resting against the lathe jaws. This is intentional. If it wasn’t, the reamer could drive the barrel towards the head stock of the lathe causing the jaws to mar the finish.

I used to use a high sulfur oil, such as Viper’s Venom or Do-Drill to cut choke tubes, I’ve switch to Tap Magic and find it works much better for this job.