Custom Mossberg 590 SHOCKWAVE build

Customizing the Mossberg 590 SHOCKWAVE

When Mossberg announced the Model 590 SHOCKWAVE it took the firearms world by storm.  This 590 isn’t a shotgun, but a firearm.  While it is a 590 chambered in 12 gauge with a 14″ barrel, it isn’t considered a shotgun under the law since it isn’t designed to be fired from the shoulder and has an overall length in excess of 26″.   This means no NFA paperwork or stamp.  Undoubtedly there are better options in self-defense firearms, but if you haven’t had the opportunity to shoot one; you should, they are an absolute blast.

As great as the SHOCKWAVE (and Remintgon TAC-14) is, I couldn’t help but customize mine up!  I decided the gun needed new sights, a choke tube and an improved safety.

This is the gun from the factory; a pretty slick little package, but you can always do better.  Spoiler alert, the next picture shows the finished project…

Here it is after I worked it over.  Before we take a look at how I did it, let’s read the 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.

I ordered the following tools and parts from Brownells for this project:

Installing an interchangeable choke tube system in the Mossberg 590 SHOCKWAVE

I began by working on the barrel.  I like the utility of an interchangeable choke tube system in a shotgun and figured that utility would carry over to this 12 gauge firearm.  Before installing tubes, the barrel needs to be assessed to see if it will work, and in this case it will.  Unlike the 500, the 590 has thick barrel walls that machine well for choke tubes. For a more detailed description of what you need to look for when assessing a barrel for choke tube installation, take a look here.

I begin by removing the barrel and wrapping the shank in some tape so I can mount it in the lathe without marking it up too badly.  Normally I’ll hold the barrel in a fixture on the lathe’s carriage, but this one is short and I plan on coating it so that didn’t seem necessary.

Since I am using a four-jaw chuck, I need to dial in the bore on the lathe.  To do this I use a dial indicator in a holder.

Next I run a Remchoke reamer into the bore.  I use Remchoke reamers on all my guns for the sake of compatibility, switching choke systems would simply mean switching the reamer and tap.   The reamer is secured in the lathe’s quill chuck and guided by a sized bronze pilot bushing.  I use plenty of oil and a spindle speed of 70 RPM.

When the edge of the reamer contacts the muzzle the barrel can be removed from the lathe.

The choke tube system now requires threads.  I use a Manson Remchoke tap.  This has a similar pilot to the reamer. Simply coat it in oil and turn it in with a large tap handle.  This type of tap isn’t backed off; just simply and slowly turned in, in one direction.  In many ways, this is the most fun part of the job.

Some compressed air to clean things up and the new choke tube fits like a champ.

Installing ghost ring sights on a Mossberg 590 SHOCKWAVE

Unlike the Remington TAC-14, we noticed the point of impact with the factory bead sight tended to be high on the SHOCKWAVE.  We figured this was due to Mossberg simply threading the bead into the barrel whereas the Remington TAC-14 had a bead base set up.  There are a number of different sighting system that would correct this.

The easiest to install would be an XS Big Dot front sight for plain shotgun barrels.  It simply epoxies on over the factory bead.  My friend put this on his SHOCKWAVE and it immediately addressed his POI issues.  It also provides a nicer sight picture and a tritium sight for low light use.

I almost went the XS big dot glue-on route, but I am a huge fan of ghost ring sights.

There are a number of solid ghost ring sighting systems out there for Mossberg 590 shotguns but one of my favorites are those made by Vang Comp.  The Vang Comp sights are expensive and harder to install than most other systems. Since I write about gunsmithing and like these sights, I decided these would be a better way to go.  If you don’t have access to a machine shop, gluing on an XS big dot might be a more prudent choice.

As I stated earlier, these Vang Comp sights are fairly complex to install.  The require soldering, drilling, threading and refinishing the firearm.  I started with the front sight, which needs to be located in the correct orientation on the barrel.  To begin I hold the action in a vise and zero a digital level on the receiver.

Next I place the front sight base towards the front of the barrel and use the level on it to make sure it is properly aligned.  I use a scribe to mark the sides of the sight on the barrel.

I’ve used a number of methods of solder on sights over the years, but have been working with LACO FAST that I ordered from Brownells.    This is a mixture of solder and flux which I find very easy to use.  

Mating surfaces need to be cleaned and prepped prior to soldering.  I used some fine abrasive to remove the factory finish from the front of the barrel.  I also filled the factory bead sight hole with some clay to prevent to solder from flowing into the barrel.

Holding the ramp in place can be difficult.  I use this spring loaded ramp soldering jig from Brownells.  With the ramp in place I heat the area with a MAPP torch until the solder flows and then allow it to cool.

Mossberg sells the 590 SHOCKWAVE with four 8-40 holes along the top.  Unfortunately, these don’t line up with the holes in the Vang Comp rear sight assembly.  I decided to use the first factory hole and drill and tap the other three. To locate the hole, I secure the receiver in the mill’s vise and use the shank of a drill to zero the DRO.  From here I’ll locate my other three holes.

I use a spotting drill to locate the holes.

And a tap drill to finish working through.

Normally I’ll tap using the mill as a guide, however, on this one I decided to use a hand held tap guide.  This small steel block ensures the tap runs straight into the hole.

Works like a champ!

The choke tube system, front sight, and rear sight mounting holes are all complete.  That means the metal work on this firearm is complete.  Time for Cerakote!

On this project I decided to use Cerakote Elite.  This is similar to the traditional Cerakote H-Series coatings, but utilize finer solids.  Use is nearly identical to the legacy product with two caveats; you need to use a special 325 mesh strainer in the cup of the spray gun, and the mixing ratio of hardener to coating is 1:18.  I selected the color “earth”.

I degrease the parts in a tray of acetone.

The parts go into the blast cabinet…

And come out looking like this.  The surfaces are ready for coating.

I hang all my parts and wipe them down with a tack cloth and give them a rinse with Brownells TCE spray degreaser.

I’ve used a number of different sprayers for Cerakote, everything from cheap airbrushes to high end HVLP sprayers.  As of now I’ve settled on using the sprayer recommended by Cerakote, the IWATA baby HVLP gun.  It works very well.  The coated parts go into the oven.  I’m using a Brownells curing oven.

With the metal finishing complete, it is time to decide on the last consideration, what to do with the safety.  The factory Mossberg 590 SHOCKWAVE safety is plastic, we can do a lot better.

These are my two favorite aftermarket safeties for the 500/590 series shotguns.  The top is the Brownells Enhanced 500/590 Safety and the bottom is the Vang Comp oversized safety.  Both are metal, both are bigger than the factory original, and either one will do the job.  For this gun, I decided to go with the Vang Comp oversized safety.

Once everything is back together, the gun looks amazing!

While I was at it, I also customized my TAC-14, more on that in the future!