TandemKross Manticore X Lower

The TandemKross Manticore X Lower for 10/22-pattern firearms is the first of its kind. It replaces a traditional stock or chassis, allowing 10/22 receivers to be mounted directly to the trigger group. From there, any standard AR-style grip can be added, and a rear rail section allows for buttstocks and braces to be attached as well. There’s so much going on with this one product, I’m cutting my intro short so I can get right into it.

Full custom 10/22 built on the TandemKross Manticore X Lower.
Full custom 10/22 built on the TandemKross Manticore X Lower.


A “10/22 lower”? Yes!

Many firearms are built on two separate halves, with an upper usually containing the barrel, and the lower having the fire control group. That would include most semi-auto handguns, as well as the most popular semi-auto centerfire rifles. In some cases, that provides additional modularity, making them more flexible platforms. The 10/22 has always been a receiver with a trigger below it, and all that dropped into a stock or chassis. The $499.99 TandemKross Manticore X turns that concept on its head. It offers modularity similar to that of the MSR (modern sporting rifle), on America’s favorite rimfire platform.

TandemKross Manticore X 10/22 Lower.
TandemKross Manticore X 10/22 Lower.


At its core is the TandemKross Manticore trigger (more on that below). Building on that, TandemKross designed the Manticore X to replace the typical stock or chassis completely. This was done by adding additional material on the top and rear which allows for the installation of grips and stocks or braces. The same pins that normally hold the trigger group inside the receiver now hold the receiver to the “lower”. Some hard rubber strips provide a little extra friction to the fit, and keep it locked up solid. And unlike an AR lower, the Manticore X is not considered a firearm, so you don’t need an FFL to purchase one.

Manticore X trigger features

Since I did a pretty comprehensive review of the Manticore trigger itself, you may want to follow that link for a refresher. The Manticore X utilizes the TandemKross Ultimate Trigger Kit, which combines a light pull with their flat-faced Victory trigger shoe. It’s adjustable for over-travel, with a pull weight that can be easily set from about 5 lbs down to 2.25. No pre-travel adjustment is necessary, as the design eliminates that completely. The result is a crisp break and short reset.

The Cornerstone Rotary Safety is ambidextrous, with levers on each side of the full aluminum housing. There is a cut in the front of the enlarged trigger guard, providing an index point for your trigger finger. A Bolt Keeper extended bolt lock makes it easy to lock the bolt open, and release it with a pull of the charging handle, or push of the button. Forward of the trigger is the Fireswitch extended magazine release. A simple push or pull of this wide, textured paddle will drop magazines for fast reloads. Note that it can also be ordered with red parts, at no additional charge.

TandemKross Manticore X 10/22 Lower with red accents.
TandemKross Manticore X 10/22 Lower with red accents.


Attachment points for grips, stocks, braces, and slings

Some manufacturer’s chassis designs will not accommodate a grip with a beaver tail. The Manticore X will take any AR grip, with or without the high beaver tail. That opens up a world of options, from lightweight nylon 12 grips to different angles, and plenty of color options too. Out back, the removable Picatinny rail section can be installed for either a straight stock or 12-degree drop. Just flip it over to change it. This clever adjustment was accomplished by simply angling the attachment surface. Similarly, the QD cup pops out and can be installed on the left or right side. It’s held in place by the same hidden screw that the rail attaches with. Between the Picatinny rail and grip mount, there’s a lot of modularity built in.

Adjustable stock angle on the TandemKross Manticore X 10/22 Lower.
Adjustable stock angle on the TandemKross Manticore X 10/22 Lower.


The TandemKross PRO Bundle for Manticore X

Although not necessary for the Manticore X to function, the PRO Bundle is an excellent kit if you’re building a rifle. And it saves you $39.98 over buying the parts separately. It’s got an M-LOK Forend which mounts using the receiver’s factory takedown screw hole. A secondary grub screw allows for proper alignment with the barrel. And of course, those M-LOK slots underneath give you a place to mount forward grips, handstops, lights, lasers, and Pez dispensers. If there is a downside, it’s that it only works with fixed barrels, not takedown models.

TandemKross Manticore X 10/22 Lower with optional PRO Bundle.
TandemKross Manticore X 10/22 Lower with optional PRO Bundle.


Next is the$139.99 Folding Picatinny Buttstock. This aluminum stock folds to the right or left, and includes a sling mount, as well as a rubber stock pad. That rubber pad aids in stability vs plain aluminum against the shoulder. Two mounting options allow it to be installed at different heights, to align with your chosen optic.

Finally, the hiveGrip. This has been a bit polarizing, from what I have seen online, but I like this grip. It’s a hard polymer with a softer rubber overmold. The result is a comfortable grip that even has an o-ringed plug for storage. Its angle seems well-suited to the Manticore X rifle builds too.

Attaching a barreled action to the Manticore X

As delivered, the TandemKross Manticore X includes a pair of their excellent KrossPins, as well as their Shock Block bolt buffer. They’re actually stored in the Manticore X, since it’s designed to be easily taken down. Remove the pins and buffer, and drop a barreled action onto the Manticore X while the hammer is cocked back. Then push the KrossPins through to keep them together. If your receiver doesn’t already have an aftermarket buffer, install the included TandemKross one. It’s that simple. This works the same whether it’s a fixed barrel receiver or a takedown.

Removal is a matter of making sure it’s unloaded, and then pushing the pins back out. I find it’s usually easier to dry fire first, as the cocked hammer can put extra tension on the pins. That may make them more difficult to remove. But the beauty of the KrossPins is that they are undersized just enough for an easy fit, while the ball detent prevents them from falling out. Best of both worlds right there. Once the barreled action is separated, store the KrossPins in the Manticore X. Also, be sure to cock the hammer and place it on safe, to avoid losing some of the small parts inside the trigger. They’re for adjustment, and it will function without them.

Build options

Since TandemKross provided their PRO Bundle for my testing and evaluation, I used the hiveGrip for all my mockups. I started with a couple of Charger builds. One uses a stubby 5-3/8″ carbon fiber barrel from Summit Precision. This would be a great suppressor host, as that barrel keeps most ammo subsonic, and using subsonic ammo, it’s very quiet. This configuration weighs just under 3 pounds with the optic and empty 15-round magazine.

Compact 22 Charger built on the TandemKross Manticore X 10/22 Lower.
Compact 22 Charger built on the TandemKross Manticore X 10/22 Lower.


Next, I used a 9.5″ barrel for another Charger build. This setup provides for more velocity, making it a good choice for ringing steel or even taking small game. That’s another Summit Precision barrel, this time about 9.5″, and topped with a TandemKross Game Changer compensator. Weight in this configuration is 3 pounds, 4.8 ounces.

Another compact 22 Charger built on the TandemKross Manticore X 10/22 Lower.
Another compact 22 Charger built on the TandemKross Manticore X 10/22 Lower.


After I did the Chargers, I attached the stock and then completed my rifle build. Since the Manticore X is such an innovative product, I felt it would pair well with an innovative receiver. So I used a Fletcher 11/22 open-top receiver. And of course, another Summit Precision barrel, this time gloss black and silver carbon fiber (matte black is shown in the photo below). Even though I have taken most of the photos on the Summit Precision website, I still think their barrels look 100 times better in person than they do in my photos. Total weight of the rifle with optic is four pounds, 9.5 ounces.

A full rifle built on the TandemKross Manticore X 10/22 Lower.
A full rifle built on the TandemKross Manticore X 10/22 Lower.


Let’s take a closer look at those weights

Three pounds for my compact Charger is pretty good. Compared to wood, that extra aluminum adds a small weight penalty. In a Boyds laminated stock with OEM trigger, it’s about 4 ounces lighter. The smaller form factor does make it difficult to shave weight though, compared to a rifle. With a different barrel, grip, and stock, it should be easy to stay well under four pounds for a rifle. I wanted to stick with the TandemKross parts, but future tinkering should yield even lighter versions. So stay tuned for some updates.

Range time

No surprises here. I’ve used the Manticore trigger for over a year, and have always been happy with the performance. So the Manticore X was no different. The rifle is light, very ergonomic, and fun to shoot. Accuracy is great, aided by the trigger set to break at the minimum, which is around 2.25 pounds. Swinging from steel to steel target brought a smile to everyone’s face. The safety is easy to manipulate, as is locking back the bolt and releasing it. Magazine swaps were quick with the Fireswitch too.

TandemKross Manticore X Lower in action at the shooting range.
TandemKross Manticore X Lower in action at the shooting range.


I kept looking for a weakness. Would the 15-round magazine fail or fall out? Nope. It worked just fine. Although the standard ten-round magazines seem to always be the better choice. Would the receiver wiggle or rattle? Not at all. Solid as a rock. Does the open magazine area cause any feeding issues? Again, not a bit. It ran reliably, even with a brand new barrel and Bentz chamber. Of my three friends who shot it on its first trip to the range, two are already planning their own builds. Which says a lot about how fun and versatile it is.

Who is the Manticore X for?

Like a lot of new and innovative products, I expected a variety of opinions when I shared photos of my builds. Some were positive, a few were negative. The positive ones were from people who appreciate “thinking outside the box”. And they realized the possible applications. Most of the negatives were centered around the MSRP of $499.99, which is understandable. At the same time, this includes the $375 trigger. Build a custom 10/22 with an aftermarket trigger, throw in a new stock or chassis, and it’s over $500 easily. The advantage here is that one trigger can easily be used for multiple barreled actions (can we call them uppers yet?).

How it started (factory 10/22 in front), and how it's going - the TandemKross Manticore X build in back.
How it started (factory 10/22 in front), and how it’s going – the TandemKross Manticore X build in back.


TandemKross sponsors some excellent Steel Challenge shooters, and I can see this being popular for a light and fast rifle. That ability to push out two pins to disassemble it should also appeal to anyone considering a takedown rifle. It offers many of the same benefits (like compact storage) without the downsides (zero drift). Similarly, if you embrace the “naked gun” concept, then it’s one trigger to use for different firearms. After removing the stock, I can throw my Charger back on for a fun pistol. Finally, some just want the newest thing out there. And this certainly fits the bill. I’m going to enjoy tinkering with different builds for a while myself.

Special thanks

As always, I’d like to thank TandemKross for providing their new Manticore X and PRO Bundle for my testing and evaluation. I’m excited to see them leading the way in new ideas for the 10/22 format. You can find the Manticore X and all their 10/22 accessories on the TandemKross website.

Well, what do you think? Love it? Hate it?  Want one? Have any of my readers built one yet?


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