Seismic Shotgun Conversions
This article focuses on converting Remington and Mossberg shotguns to the Seismic Shooting System. I’ll cover the various models to help you choose which shotgun would work best for you, or, if you already have a shotgun, you will learn what’s involved.
Most conversions will fall into 1 of 4 categories.
1. Full stock shotguns, for hunting, general purpose, and tactical.
2. Manufactured traditional pistol grip shotguns with 18” barrels
3. Mossberg Shockwave with 18” barrel.
4. Remington Tac 14 and Mossberg Shockwave with 14” barrel
Remington and Mossberg Conversions
My first PGO shotgun conversion was built from an old Mossberg 500 with a wood stock. I had this shotgun for over 30 years and rarely shot it. After a trip to a skeet range, I realized again why I never shoot it and had no interest in ever shooting it again. I had just cleaned it for the last time when I decided to convert it into a pistol-grip shotgun, and that’s what I did. It would be the first of hundreds of conversions and builds I would complete over the next 7 years. And it marked the beginning of what would eventually become Semitic Shotgun Innovations.
One day, I picked up a Remington 870, which became my preferred shotgun for PGO conversions. In those early days, I made my pistol grips from the butt stocks. I could make grips far more comfortable to shoot than anything I could buy, and I enjoyed transforming hunting shotguns into tactical PGOs.
If you have an old shotgun sitting in the safe you no longer shoot, this is also a good option if you're handy with tools and woodworking. With the Remington 870, it’s easy to make a grip from the butt stock that performs well with the Seismic Shooting method. The Mossberg 500, on the other hand, is inherently more difficult to make a pistol grip from the stock that performs as well as the Remington's.
Today, we’ll discuss the difference between these two platforms and why you may choose one over the other.
Remington or Mossberg, which one is best for you?
If you're considering a DIY PGO conversion, choosing one over the other has nothing to do with quality or reliability. As far as I’m concerned, both are highly reliable, and you could not go wrong with either. However, when it comes to pistol-grip conversions, there is one difference to consider.
I found the Remington's ergonomics inherently better suited to pistol-grip shotguns. It has to do with the trigger's position relative to the grip. The Remington's trigger guard extends all the way back to the edge of the receiver; the Mossberg trigger is positioned 1” inward. The result is a 1” longer trigger reach with the Mossberg. This may not sound like much until you consider that the human trigger finger is only about 3” long.
Because of this, I could design grips for the Remington that performed significantly better. I wanted a grip that gave me comfort, control, and accuracy. I achieved that with the Remington 870. After I discovered this, I shifted all my efforts to the Remington grip design and, after many prototypes and shooting 1000s of rounds in testing, ultimately designed the perfect grip. Years later, I returned to the Mossberg and gave it another shot at creating a comfortable grip. I was amazed that manufacturers still make the same type of grips for both platforms, a one-size-fits-all approach, even though the geometry is radically different. I started over from square one. I knew what worked with the Remington was not going to work on Mossberg.
I needed a new design, and after several prototypes and tests, I finally created a grip that performs as well as the Remington. However, they each give you a different shooting experience. I’ll cover this more extensively in upcoming videos.
The big takeaway on this is: If you want to build a PGO shotgun conversion and make your own grip from the buttstock, choose the Remington 870. Good results are more easily obtained.
If you're going to purchase a Grip from Seismic Shotgun, your choice comes down to what shotgun you like best. We have solved the trigger reach issue with new grip designs, and both the Remington and Mossberg grips now provide exceptional comfort and control. However, they do give a distinctly different shooting experience.
The only consideration would be that the feel and ergonomics are different. In general, if you’re a woman or have smaller hands, I would go with the Remington. If you have larger hands, it just comes down to preference in choosing a shotgun.
If you have an affinity for wood, as I do, but don’t have the skill or tools to make your own grip, you’ll be happy to know that the Seismic accessory kits will be available in wood as well.
Full stock conversions and vent rib barrels
Back in my early days of PGO conversions, these shotguns were cheap and plentiful. One of my favorite PGO shotguns is a Remington 870 Wingmaster that I picked up for $200, and to this day, it remains one of my favorites. The action is smooth and reliable. It runs without fail, and the 18-inch barrel delivers consistent accuracy at 100 yards. What more could you want from a PGO shotgun?
There are a few things to consider when choosing a full stock shotgun for PGO conversion.
If you already have a Mossberg 500 or Remington 870 and don’t shoot it, why not transform it into something new? Something you will use.
Capacity:
The hunting version of the Remington 870 comes with 4 +1 capacity. What's great is it's simple: add a 2-shell mag extension and boost it to a 6+1. In my opinion, 7 rounds in a PGO shotgun that’s just 4” longer than a Tac 14, is the better option.
The Mossberg 500 comes with a 5+1 capacity, and there are no options to add mag extensions.
Barrels and Rails
These shotguns come with Vent Ribbed barrels. Personally, I like the Vent Ribbed barrel. It’s minimalistic and provides an integrated platform for mounting optics. There are two options to attach the Seismic Rib Rail: one requires drilling and tapping the rib, and the other clamps on with set screws. You also have the option to add an Amega Scout Mount rail to the vent-rib barrel, which also doubles as a heat shield. Unfortunately, these are currently unavailable, and we are working on new options.
One reason you might not consider the Vent-Ribbed barrel is that it doesn't come in a thick-walled or heavy-duty version. But unless you're shooting in hardcore tactical applications or you’re a professional, I wouldn't be concerned about it. I have put these barrels through extreme conditions, run 1000s of rounds through them, repeatedly firing over 100 rounds nonstop, making them excessively hot, and banged them around during rigorous training. I can attest to their durability, and for most shooters, they will serve you well.
Review: The full stock conversion consists of:
· Cutting and crowning the barrel
· Mounting your barrel rail choice
· Installing the Seismic Grip
· Mounting the SRM Cheek Weld
Some of these may require drilling, tapping, or gunsmith work.
Manufactured Pistol Grip Shotguns with 18” barrels
Both Remington and Mossberg have their versions of pistol-grip shotguns that come standard with an 18” barrel. They typically come with a traditional palm-pounding pistol grip. The barrels on these models are smooth and require mounting an Amega Scout Mount rail or a similar rail. The Seismic grip is easy to change out. All you need to complete the conversion is to mount the RM Weld.
Mossberg Shockwave with 18” barrel
The Mossberg Shockwave is a 590. The Seismic Grip and RM Weld will attach the same way as on the 500. The 590 does have a heavy-duty barrel and requires a different barrel rail option. This will be an integrated rail or bolt-on.
Other Firearms: Remington Tac 14, Tac 13, Mossberg Shockwave, and Aftershock.
These models require a longer grip or barrel modification to remain legal.
Warning: You CANNOT attach the Seismic Pistol Grip to any of these shotguns without first making modifications. If you do, your shotgun will no longer be legal because the new grip shortens the overall length to under the legal 26”.
To do this legally, you must increase the barrel length. The easiest way is to add a muzzle break. This reduces recoil, gets you over the 26” mark, and allows you to add a shell extension. With my Tac 14, I also soldered the rail onto the barrel.
Another option we are considering is to design a longer Seismic Grip that retains the advantages of the current designs.
We are also working on other rail options for these short-barreled firearms. As the Seismic Shooting System becomes more popular, maybe Remington and Mossberg will consider building these with integrated rails and a muzzle brake; we will see.
For descriptions, applications, and installation notes on the Seismic Accessories, see the PGO Conversions page on the website.
Our aim is to educate people about the Seismic Shooting System before accessories become available. This is an entirely new way to engage with your shotgun; it takes time to adapt and learn. There are also safety protocols and other information you should know before deciding whether a Seismic conversion is for you! Stay in the loop with our website, newsletter, and the new Seismic YouTube channel.
