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Best Modular Handgun

5D Tactical - 3rd Feb 2023

Well, it’s 2023 now and the name of the game for everyone not well, me, is modularity. A modular gun seems to be on everyone’s mind these days. Options for days, be it a pistol frame, barrel length or anything one could think of really! SO with everyone and their grandmas trying to break into the new and hot modular gun market, which ones should we choose? What features do we really need in a modular pistol? Grab your favorite juice box and some pretzels and let’s dive right on into it folks!

What is a modular handgun?Sig P320 Platform

Sig P320 Modular Handgun. Note - the fire control unit in the center of the photo is the serialized gun, all the other parts can be changed. Photo Credit: Gat Daily

When someone says "wow, that's a modular pistol." That usually means that there is a lot of aftermarket support for that particular handgun platform. Or it may be as simple as the frame being able to offer different sized back straps to accommodate for different shooters' hand sizes.

It's also the term used to describe fire control units (FCU) which are serialized and legally considered to be the gun themselves. The reason being for this is that with the FCU being the actual gun, a modular pistol is able to have nearly every part swapped out to better fit the shooter and the shooter’s needs. Some parts on the gun commonly swapped out on a modular pistol around the FCU include:

  • Pistol frame
  • Barrel
  • Trigger
  • Slide

Well, we might say, that sounds fantastic, but do we really need it? The answer dear reader, is yes, and the reason? Because we can.

What are the benefits of a modular handgun system?

As we’ve already touched on above, being able to interchange everything from the handgun frame to the slide offers a lot of benefits. Prefer a full size pistol frame for a duty weapon or for the range? Simply swap it out. Need a concealed carry weapon? Swap the compact grip and slide assembly back onto the FCU and we’re good to go.

Having a modular pistol system simply means one gun can have many accessories and fill multiple different roles. Long term benefits might include just being able to change a modular pistol into several different types of weapons without needing to spend cash on multiple weapons. This can equal big savings in the long run!


  • Ability to change the gun for the shooters needs
  • Overall savings by just buying components and not more guns for other purposes


  • For some shooters, the weapon customization can be rather addicting!

Which Modular Handgun system Should I choose?

As with any weapons system, this is always going to be subjective. However, the beauty of the modular pistol is that it can be so quickly and easily swapped out to become a better tool for the mission or a different shooter. This level of customization and modularity can make a lot of difference!

GST-9 Mod 1GST-9 MOD1 Sage Build

Photo Credit: 80 Percent Arms

We know this is a kit we sell that the shooter will have to build themselves. We get it, but hear us out. The GST-9 might be one of the, if not THE most modular systems on the planet. Every part can be swapped out with Glock 19 Gen 3 components, and the grips can even be size adjusted without having to disassemble the entire thing! What else makes the GST-9 Mod 1 Special?

  • Modular frame gives you the possibility of a 19, 19X, 19L, & 17 size weapon system in a single 4-in-1 platform
  • Compatible with Glock 19 3rd generation parts, holsters, & aftermarket accessories. GST-9 is the first and only 80% lower that is compatible with Glock holsters
  • Ergonomic features include an undercut trigger guard, high beavertail, glove bevel, scalloped mag release, no finger grooves, & newly redesigned gas pedals as standard
  • Premium internal rail components extended 3X, made of stainless steel, with multiple coating options
  • Easily ships to your door & completes in minutes

Sig Sauer P365 SeriesSig P365 Macro with Red Dot Sight

Photo Credit: Ammoland

The Sig P365 series has become wildly popular in recent times and for good reason. The P365 is an easily concealable platform with multiple frame, barrel and slide options right from the factory. The newest of these is the Sig P365 XMacro - which holds a whopping 17 + 1 rounds of 9mm in a concealed carry gun with a built in compensator and right about an inch thick! The Sig P365 XMacro is optics cut from the factory and it is really a sweet gun!

Don’t need the compensator? Fear not! Simply grab the Sig Sauer P365 XMacro frame and swap it onto a P365XL and now all that capacity is in an even smaller package.

Sig Sauer P320 SeriesSig P320

Photo Credit: CDH2A

Recently adopted by the U.S. Military, the P320 needs very little introduction. Again the fire control unit is the serialized, actual gun itself. Swap out the full size Sig P320 Frame for a compact frame and we’ve got a compact handgun that is similar in size to most average carry guns. Not sure which slide and frame sizes are best? Sig P320 Frames are relatively inexpensive and readily available, making this a formidable weapon in the modular gun world. Many parts of the Sig P320 are customizable and can even be ordered built to whatever specs are desired right from the factory online store.

Zev Technologies OZ9Zev OZ9

Photo Credit: Zev Technologies

A newer contender to the modular pistol world are Zev Technologies. Originally known for Glock upgrade parts, Zev Tech now makes entire guns such as AR-15 platform rifles and handguns, as well as an array of upgrades for the Glock still. The Zev Technologies OZ9 is their newest handgun and it is a Glock aficionado's dream.

The Zev Tech OZ9 is available in several models to fit any shooter’s needs and is reminiscent of the Glock 19 in the Compact size, with available grip modules to bring the modular gun to sizes and specs that are similar to the Glock 17 and 19X. As with the above guns, simply swap out the Zev Tech OZ9 pistol frame with whatever size pistol frame works best for the current mission - be it a range day, concealed carry weapon, or duty gun. Need some more bling? The Zev OZ9 Elite is their top of the line model and has features only found in very high-end custom handguns usually. All of this does come at a price though - expect to pay around $1800-2000 for a Zev OZ9 Elite model.


ZRO Delta One

Photo Credit: Black Box Customs

A newer player in the modular handgun market, ZRODelta ONE is a new full pistol or pistol build kit that brings some interesting features. With replaceable front and back straps, dust cover lengths, mounting plates for optics, magwells and slide assemblies, the ZRODelta ONE is an interesting one to be sure. Available in compact, full size and race (competition) sizes, the ZRODelta ONE is even rumored to soon be able to detach the frame from the modular pistol and slide that frame onto a proprietary AR-15 lower to be used in a rifle configuration. Whether or not this is simply a gimmick remains to be seen, but utilizing a handgun frame to slide onto an AR15 seems a bit gimmicky in our book.

Start your next pistol build with 5D Tactical!

We hope this helped lend a little insight into the world of the modular handgun. While the idea may have seemed a bit foreign at first, there are truly a lot of benefits to the idea of a modular pistol! Check out the GST-9 Mod 1 a little more and consider building the perfect, custom modular pistol.