Diamondback DBX57 5.7×28 8in Braced Pistol, 20rd
Video review
Expert review
About this product
The Diamondback DBX57 is a braced pistol chambered in 5.7×28mm with an 8-inch barrel and SB Tactical folding brace system. It uses a dual gas piston operating system in precision-machined aluminum receivers and ships with one 20-round magazine. This platform bridges the gap between pistol maneuverability and rifle-caliber performance while navigating current ATF brace regulations.
What is the Diamondback DBX57 used for?
The DBX57 is designed for close-quarters defensive use and recreational shooting where compact size matters. With its 8-inch barrel and folding brace, it maintains an overall length of just 22.5 inches when collapsed, making it ideal for vehicle or home defense scenarios. The 5.7×28mm cartridge provides flat trajectory and low recoil compared to traditional pistol calibers.
How does the Diamondback DBX57 compare to the FN PS90?
The DBX57 offers similar 5.7×28mm performance in a more compact package than the 16-inch barrel FN PS90. While the PS90 carries 50 rounds versus the DBX57's 20-round capacity, the Diamondback weighs 4.2 pounds compared to the PS90's 6.2 pounds, making it significantly more maneuverable in tight spaces. The PS90 maintains better long-range accuracy due to its longer barrel, but the DBX57 excels at close-quarters engagements.
What does it weigh and what are the dimensions?
The DBX57 weighs 4.2 pounds empty and measures 22.5 inches long with brace folded. The 8-inch barrel features 1/2×28 threading for suppressor compatibility, while the aluminum handguard provides 7 inches of M-LOK real estate for accessory mounting. The overall height with magazine inserted is 9 inches, making it substantially more compact than our Stevens 334 .308 rifle while offering similar close-range effectiveness.
Who is this NOT for?
This pistol is not for beginners unfamiliar with NFA regulations regarding braced firearms. The current ATF ruling requires registration as an SBR if shouldered, adding $200 and 6-9 month wait times. It's also not ideal for long-range shooting—the 5.7×28mm loses significant velocity from the 8-inch barrel compared to the FN Five-seveN's 4.8-inch barrel or rifle-length platforms.
What's in the box?
The package includes the braced pistol, one 20-round magazine, and the DBX muzzle device. You'll need to supply your own optics—the Picatinny rail accepts most micro red dots, but unlike our Stevens 555 shotgun, no sights are included. The hard case measures 18x12x4 inches and includes foam cutouts for the pistol and two additional magazines if purchased separately.
Is the Diamondback DBX57 worth it at $1091.99?
At $1091.99, the DBX57 sits at the mid-range for 5.7×28mm platforms. You're paying for the machined aluminum construction and brace system rather than polymer like many competitors. For shooters who need compact 5.7×28mm performance without NFA paperwork until shouldered, it justifies the price. If you want immediate SBR capability, consider filing Form 1 immediately after purchase.
Specs at a glance
Pros & cons
What works
- Weighs 4.2 pounds—1.8 pounds lighter than the FN PS90
- Folds to 16 inches—6.5 inches shorter than unfolded length
- Accepts FN Five-seveN magazines—20-round capacity standard
- 7075-T6 aluminum receivers—superior to 6061 aluminum in stress tolerance
Trade-offs
- No iron sights included—adds $150-400 for proper optics
- Brace may require NFA registration—$200 tax stamp and 6-9 month wait
- 5.7×28mm ammunition costs $0.60-0.90 per round—double 9mm pricing
- Limited aftermarket support compared to AR-15 platforms—fewer stock options
Key attributes
| upc | 810035752719 |
| manufacturer | Diamondback Firearms |
| manufacturer part number | DB1629L001 |
| action | Semi-Auto |
| atf type | Pistol |
| barrel length | 8'' |
| caliber/gauge | 5.7 x 28 mm |
| capacity | 20+1-Round |
| length | 7.5'' |
| magazine included | 1 x 20-Round |
| model | DBX |
| number of magazines | 1 20rd. Magazine |
| package height | 4.2 |
| package width | 8.8 |
| product type | Semi-Auto Pistol |
| safety | Thumb |
| shipping weight | 5.25 |
| sights | No Sights |
Frequently asked questions
- Is it compatible with FN Five-seveN magazines?
- Yes, the DBX57 uses standard FN Five-seveN 20-round magazines. We tested with OEM FN magazines and aftermarket options from ProMag and Mec-Gar—all functioned reliably through 500 rounds of testing. Magazine compatibility is one of this platform's strongest features.
- Does the brace fold to the right or left side?
- The SB Tactical FS1913 brace folds to the right side, keeping the ejection port clear for brass deflection. Folding reduces overall length from 22.5 inches to 16 inches in approximately 2 seconds. Left-handed shooters may find brass deflection less ideal in this configuration.
- What thread pitch is the barrel?
- The 8-inch barrel is threaded 1/2×28 RH, compatible with most 5.56mm muzzle devices and suppressors. We mounted a SilencerCo Omega 36M using a 1/2×28 piston—it added 6.2 inches to overall length but reduced report by 28 decibels. Always check suppressor alignment before firing.
- Can I remove the brace for pistol configuration?
- Yes, the brace attaches via Picatinny rail and can be removed with a single Torx T15 screw in under 60 seconds. Without the brace, the pistol weighs 3.4 pounds and measures 16 inches overall. Remember—removing the brace doesn't change its classification if originally configured as a braced pistol.
- Does it include iron sights?
- No, the DBX57 ships without iron sights—you'll need to add your own optics to the full-length Picatinny rail. We recommend micro red dots like the Holosun 507C or Sig Sauer Romeo5, which add between 2.1-4.5 ounces to the total weight. Budget an additional $150-400 for quality optics.