KelTec Sub 2000 Gen 3 in 5.7x28mm | Review

This article first appeared on AmmoLand News on July 11, 2025 and appears here now with fresh updates.

I’m an unashamed KelTec fan. They seem to be one of the few companies doing neat and weird stuff. One of their classic, weird, but effective designs is the KelTec Sub 2000, also known as the Sub 2K. It’s now in its third generation. I’ve owned one of each generation, and when the Gen 3 came out, I liked the upgrade but didn’t need another 9mm carbine. Then KelTec released the 5.7x28mm version, and it caught my attention.

The 5.7×28 isn’t a traditional pistol round, but it’s not a traditional rifle round, either. FN designed the 5.7x28mm for lightweight, SMG-like guns for a Personal Defense Weapon project. The cartridge was designed to defeat soft armor and provide greater overall range than a 9mm cartridge. The 5.7 looks like a modern rifle round, just shrunk.

It features a spitzer bullet and bottleneck design in a small overall footprint. What interested me most was a lightweight carbine option that was downright affordable. The KelTec Sub 2000 has always been affordable, and for less than $400, I was out the door with my Sub 2000 and my first 5.7x28mm rifle.

The KelTec Sub 2000 Gen 3 – Why 5.7x28mm?

Live Inventory Price Checker

	Kel-Tec Rifle Sub2000 Gen 3 16.1" 9mm Glock Mags 15rd, Green - SUB2K9GLKGRN	Palmetto State Armory	$ 456.99 $ 414.99
	Kel-Tec Rifle Sub2000 Gen 3 16.1" 9mm Glock Mags 15rd, Green - SUB2K9GLKGRN	Palmetto State Armory	$ 539.99 $ 449.99
	Kel-Tec Rifle Sub2000 Gen 3 16.1" 9mm Glock Mags 15rd, Green - SUB2K9GLKGRN	Palmetto State Armory	$ 456.99 $ 414.99
	Kel-Tec Sub2000 Gen 3 9mm 16.1" 15rd Rifle, Black - SUB2K9GLKBLK	Palmetto State Armory	$ 499.99 $ 329.99

The Sub 2000 famously folds in half to reduce the overall length to about 16 inches. The folding design makes this one of the most compact rifles on the planet. It’s incredibly small and lightweight, making its handiness its main strength. It’s easy to stash and store, and it makes for a great truck gun, a camping gun, or even a self-defense rifle.

With those strengths in mind, I think the 5.7x28mm round helps emphasize the rifle’s handiness. The 5.7 round complements all of the Sub 2000’s strengths to make the rifle even handier. The round offers more range than a 9mm round and has been proven to be fairly effective.

It doesn’t outperform a 5.56 by any means, but can you put a 5.56 round in a rifle this light, compact, and affordable? Plus, it folds! The 5.7 gives you around 200ish yards of effective range, especially when paired with some form of slightly magnified optic.

The small projectile is a solid penetrator, and I feel that a 5.7 can be a good low-recoil defensive option. There are better options, but for folks who lack upper body strength and are recoil-sensitive, the 5.7 is going to be tough to beat, especially from a rifle.

To me, the Sub 2000 Gen 3 in 5.7 is like a modern M1 Carbine.

What’s New With the Gen 3?

The KelTec Sub 2000 Gen 3 features a few fixes compared to the older generations of the Sub 2000s, namely the ability to use optics. The big change from the Gen 2 to the Gen 3 was native optics-ready capability. The Gen 2 had a rail, but throwing an optic on it would prevent the rifle from folding.

Various optics mounts were created to avoid this, and I’m partial to the MCARBO option on my Gen 2. The Gen 3 integrated a handguard that rotates when you fold the rifle. It rotates to the right or left, and it’s the user’s choice. This allows the top of the handguard, with the optic in place, to rotate the optic out of the way and fold the gun.

This does mean the gun ditches iron sights entirely, but I’m betting most people won’t miss them. I do wish the Sub 2000 would rotate 180 degrees to place the optic on the same plane as the pistol grip. It currently sticks out to the side and creates a much bulkier package than necessary.

The barrel is threaded, and numerous .22 cans are 5.7 rated but double-check before you light it off. Subsonic 5.7 exists and isn’t tough to find. The Gen 3 Sub 2000 has all the same features as the Gen 2 Sub 2000. This includes the partial M-LOK rail, the adjustable stock, and a ton of sling points.

The use of the 5.7x28mm round makes this an extremely lightweight rifle, at only 4.36 pounds. The 5.7 models use the FN Five-Seven pistol magazines, so 20 rounds are the standard. Sadly, KelTec decided to go with a ProMag as the included magazine. ProMag, just say no.

Loading Up the Gen 3 Sub 2000

I equipped my Sub 2000 Gen 3 with a Primary Arms MicroPrism with 3X magnification. If I’m shooting 5.7, I might as well take advantage of it. These MicroPrism optics have less than optimal eye relief, and the optic mounts fairly far forward on the gun’s rail.

With the optic mounted, I have to tap into my Marine Corps roots and choke up on the gun. We used to call it “nose to the charging handle” when dealing with ACOGs on the M16A4. We have to keep that same energy with this setup. Choke up on it a bit, and you get a full view through the optic.

I zeroed at 17 yards, which is odd, but there’s a reason. According to the MPBR calculator, a zero at 17 yards will carry out to 150 yards and even out to 170 yards with a little elevation. With a 17-yard zero, with this optic and ammo, even at 200 yards, we are only seeing 10 inches of drop.

This works quite well. I can hit a 10-inch gong at 150 yards from an offhand standing position. I can most certainly lob rounds into an IPSC steel target at 200 yards by just aiming at the head zone and letting them drop into the chest. In terms of raw accuracy at 100 yards, the gun is fine with 3 MOA groups on average with cheap Fiocchi ammo.

The 5.7mm round is quite accurate and flat-shooting. The KelTec rifle platform itself has some limitations.

Shooting Straight – Problems

Let’s remember that the barrel on this rifle folds away from the receiver and is encased in polymer. It’s not a free-floating design, and it’s not designed to offer you a ton of precision. The accuracy also degrades quickly when it heats up.

As the Sub 2000 gets hotter, we see our groups start to open up significantly. I shot a five-round group at 50 yards, then shot about 80 rounds in 20 minutes and reshot that 50-yard group. The group size increased by a factor of four.

No one will brag about this trigger and its weight, creep, and grit. It’s like plastic rubbing on plastic. It’s fine for the PCC and most similar platforms, but it starts to become annoying when you’re shooting at 100 yards and beyond.

Running Raw

The Sub 2000 in 5.7 handles a whole lot better than the original Sub 2000s. The 9mm and .40 S&W variants tend to have snappy recoil with a blowback action and harsh recoil. The 5.7x28mm round has almost no recoil; it’s much lighter with no snap to it.

It’s still direct blowback, but due to the lighter 5.7 design, it’s not nearly as bad as other cartridges. Additionally, the recoil spring is much lighter, which means less resistance when charging the weapon. Anyone can ready this weapon.

You can shoot the 5.7x28mm Sub 2000 with ease and deliver a lot of rounds on target swiftly. It’s like unleashing an angry swarm of bees. You can press the trigger rapidly and drain the entire 20-round magazine on target without ever losing control. From the low ready, Bill Drills kept themselves in the 1.7-second range.

If you want an extremely low-recoiling, lightweight rifle for home defense, the 5.7 Sub 2000 would be tough to beat. Ditch the prism for a red dot, and you have a capable close-range firearm.

Worth the Squeeze?

The only reliability issues I had with the gun came when using the ProMag. When fully loaded, it would often choke on the first few rounds. I purchased a handful of FN magazines and have had zero malfunctions when using quality magazines.

Ultimately, the KelTec Sub 2000 in 5.7x28mm might be the best Sub 2000 out there. It’s certainly the lightest, the most capable at longer range, and has the lightest recoil. The ammo is admittedly pricier than 9mm, but the price seems to be coming down, with fifty-round boxes commonly selling for around $20.

If you can spare the extra money for the ammo, the Sub 2000 in 5.7 is the way to go for folding carbines. AmmoToGo was kind enough to provide ammo for this review, and they have some rather affordable options. Hopefully, S&W responds with a 5.7 FPC, and we can get a few more affordable 5.7 carbines.

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About Travis Pike

Travis Pike is a former Marine Machine Gunner, a lifelong firearms enthusiast, and now a regular guy who likes to shoot, write, and find ways to combine the two. He holds an NRA certification as a Basic Pistol Instructor and is the world’s Okayest firearms instructor.