Kel-Tec SUB2000 Gen3 5.7 vs RTAC RT15 5.7: Fold or Fifty?

One folds in half and carries easily. The other is an AR with a very large magazine. Both shoot the same small, fast cartridge, and the choice is about what you do with them.

Two answers to the same cartridge

5.7x28mm is a small, fast cartridge: a light, narrow bullet in a bottlenecked case, originally developed by FN. It produces gentle recoil and a flat arc over short distances. Two carbines in this catalog chamber it, and they take very different approaches.

The Kel-Tec SUB2000 Gen3 in 5.7x28mm is a folding carbine with a 20-round magazine according to the listing. The RTAC RT15 in 5.7x28mm is an AR-pattern rifle, listed as a 16-inch model with a 50+1 capacity. The choice is mostly about the problem you want to solve.

The packable one: SUB2000 Gen3

The SUB2000 is known for folding in half, which turns a carbine into a compact package that fits in a small bag. That is the reason people buy it. If you want a lightweight, easy-to-store carbine for a vehicle, a cabin, a boat or a range bag, this is the design that makes sense.

Confirm the weight, the folded dimensions and the sights or optic options on Kel-Tec's pages. Also ask what magazine pattern it takes, because 5.7x28mm carbines vary. Our network site BuyMoreGuns covers the maker's range in its Kel-Tec lineup guide, and HomeDefenseGuns discusses the SUB2000 in its roundup of PCCs beyond the Ruger.

Strengths:

• Folding makes storage and transport easy.
• Light recoil from a light cartridge.
• Simple controls.

Limitations:

• Folding designs trade some stability and aftermarket depth for compactness.
• Magazine capacity is smaller than the RT15's listing.
• Optics and accessories are more limited than on an AR.

The big-magazine one: RT15 in 5.7

The RT15 in 5.7x28mm applies AR-style handling to the same cartridge. Per the listing, it is a 16-inch rifle with a 50+1 capacity. If you already shoot AR-pattern rifles, the controls are familiar: you will recognize the charging handle, safety and magazine release. A rail and AR-style optics mounting make it easy to put a red dot on.

For its 5.56 sibling, our RT15 review covers inspection and break-in advice that applies equally to the 5.7 version.

Strengths:

• AR ergonomics and optics mounting.
• A very large magazine capacity per the listing.
• A conventional, rifle-like shape.

Limitations:

• A 50-round magazine is long and heavy, affects how the rifle balances and rests on a bench, and complicates shooting from the ground.
• Ammunition and magazine supply for 5.7x28mm is narrower than for 9mm or 5.56.
• The RT15 name is shared with the 5.56 version, so make sure you are comparing the right listing.

The 50-round argument

A 50-round magazine sounds like a pure benefit. Consider the trade-offs.

Fun at the range, awkward elsewhere. Fewer reloads means more shooting time. A magazine that long, however, hangs well below the rifle, and shooting from a bench or prone can get in the way.

Legal limits. Many states and localities restrict magazine capacity. A 50-round magazine is not lawful everywhere, and some places restrict it by the date of manufacture or purchase. Check your state and local law before buying.

Reliability questions. Large-capacity magazines are more demanding for makers to get right. The spring has to push a long column of cartridges, and the cartridge's shape matters. If you buy one, test it with the ammunition you plan to use before depending on it.

Practical shooting. For plinking, large magazines are enjoyable. For any task where you need to carry the rifle, shoot from awkward positions or keep it stored compactly, a smaller magazine is more practical.

Head-to-head

About the cartridge

5.7x28mm has virtues and limits.

Virtues. Mild recoil, a flat trajectory over short distances, and a lot of rounds in a magazine.

Limits. Ammunition is less widely stocked than 9mm or 5.56 and is typically costlier per round. The cartridge was designed for a particular type of use and is not a general purpose hunting round. Confirm what your state requires for any game before considering it. Our network site DefensiveHandgun has a look at 5.7x28mm in pistol form that covers the cartridge's characteristics.

Planning around ammunition supply

The cartridge is the part of this decision that has the longest tail. 5.7x28mm is stocked by fewer sources than 9mm or 5.56, and the loads available vary. Before you buy either rifle, look at what is actually sold near you and online, and think about:

• Variety. Are there loads for practice and for other uses, or only one or two products?
• Consistency. Do the loads you can find shoot reliably in a carbine and, if relevant, in a handgun?
• Local rules. Some places restrict certain ammunition types at ranges.
• Storage. Ammunition should be stored cool, dry and secure.

If supply looks thin where you live, that is a good reason to consider a 9mm carbine instead.

Sights, optics and zero

Both rifles are used at short to moderate distances, which suits a small red dot. Zero on a stable rest with the ammunition you plan to use. Because the cartridge is light and fast, it shoots flat over short distances, but the bullet is also light enough to be affected by wind and barriers, so do not assume a zero is good at all distances. Check the ammunition maker's published data for your load and verify at the distances you care about.

The SUB2000's folding design may limit the optics and mounting options. Confirm Kel-Tec's rail or mount arrangement before choosing an optic. The RT15's AR-style rail simplifies the question.

Range behavior with a large magazine

A 50-round magazine changes the way you manage a range session. A few habits help:

1. Load with care. Large magazines can be stiff to load by hand, and you should follow the maker's guidance.
2. Keep muzzle discipline, because a long magazine alters where your hands go and how you hold the rifle.
3. Respect the range rules. Some ranges limit rate of fire or magazine size.
4. Clear malfunctions methodically, since large magazines can be harder to remove.
5. Do not leave a loaded magazine in a stored rifle.

These are general habits and not product claims.

Buying checklist for either rifle

1. Confirm the magazine pattern and where spares come from.
2. Check the legal status of the configuration in your state, including magazine capacity limits and any rules about folding stocks or large magazines.
3. Find ammunition before you buy the rifle. If you cannot source 5.7x28mm easily where you live, think again.
4. Read the manual's ammunition guidance.
5. Plan an optic. A small red dot suits both.

Which one

• Pick the SUB2000 Gen3 if you value compact storage, a vehicle or travel gun, and a gentle cartridge.
• Pick the RT15 in 5.7 if you want AR handling, an optic-friendly rail and a very large magazine, and your state allows it.
• Pick neither if you want a general-purpose carbine; a 9mm carbine such as the one in our Saint Victor 9mm review uses a far more available cartridge.

Both transfer through a licensed FFL, and the magazine-capacity and configuration rules for your area are yours to verify.

Editorial note: This is an independent editorial overview built from manufacturer specifications and publicly available information. We have not performed hands-on testing of the products discussed, and nothing here is a performance guarantee. Verify specifications, compatibility and legality for your own situation.

Affiliate disclosure: Some links on this page are affiliate links to Ammunition Depot. We may earn a commission if you buy through them, at no extra cost to you. Our editorial choices are not influenced by commissions. Check current price, stock and specifications directly with the retailer.