12.5″ 5.56 NATO Quattro-15 Monobloc® A5 Pistol
Mid-length 5.56 NATO · 11.7″ M-LOK handguard · VLTOR A5 · SB Tactical SBA5® brace · black
12.5″ HM Defense Monobloc® barrel with the standard A2 Extended Flash Hider in Black Cerakote®, thermal fitted to a SOTM4 MOD-0 forged upper receiver with an 11.7″ SOT Wedge-Lock M-LOK handguard, paired with a Desert Tech Quattro-15 lower receiver with a Radian Talon ambidextrous selector, a LaRue Tactical MBT-2S straight-bow trigger (the curved bow is standard), a VLTOR A5 receiver extension and A5H2 buffer with a Forward Controls Design CN5F extended castle nut, an SB Tactical SBA5® pistol stabilizing brace, a B5 Systems Type 23 grip and a Desert Tech QMAG-53 quad-stack magazine. Upper, handguard and lower black anodized.
// Specification
| Model | 12.5″ 5.56 NATO Quattro-15 Monobloc® A5 PistolSKU QTR15-MB-B125-H117M-BLK-P |
|---|---|
| Series | Quattro-15 · Direct impingement (DI)Pistol |
| Chambering | 5.56×45mm NATO.223 Remington compatible |
| Barrel | 12.5″ HM Defense Monobloc®Standard bore · 4150 chrome-moly steel (CrMo) · balanced taper profile · Black Cerakote® |
| Twist | 1:8 |
| Muzzle thread | 1/2×28 |
| Gas system | Mid-lengthMid-length at 12.5″ through precision port sizing · gas block milled into the barrel blank: no separate block to clamp, pin or shift |
| Muzzle device | A2 Extended Flash Hider, Black Cerakote®Standard, shown. Optional: 4-port hardened flash hider, Faxon MuzzLok® Gunner 3-port 5.56 steel brake or Faxon MuzzLok® stainless steel Plan B brake |
| Suppressor | Suppressor-ready with any of the Faxon MuzzLok® brakesThe MuzzLok® removes to leave the 1/2×28 thread for a direct-mount suppressor |
| Upper receiver | SOTM4 MOD-0 forged, 7075-T6, black anodizedBarrel thermal fitted: no retaining compound, no bedding |
| Forward assist | YesPhosphate finish |
| Handguard | 11.7″ SOT Wedge-Lock M-LOK, black anodizedFree float · twin-lug wedge lock to a steel barrel nut, anti-rotation tabs · full-length top Picatinny rail |
| Bolt carrier group | SOT Enhanced HMB™, Black NitrideStandard · arrow-indexed cam pin · index-marked gas key. Optional, +$149.00: Young Manufacturing M16 Chrome BCG with HMB™ bolt (supplied as Young build it, without SOT's cam pin or gas key marks), or Microbest Super-Stake C158 all-chrome BCG, heavy-duty stake, with chrome HMB™ bolt |
| Charging handle | Breek Arms WARHAMMER Mod2Ambidextrous |
| Ejection port cover | Laser-engraved caliber markingsInside and outside the cover |
| Lower receiver | Desert Tech Quattro-15, black Type III hard-coat anodizedMachined from a 7075-T6 aluminum forging |
| Lower rollmark | MULTI-CALThe pistol is chambered 5.56 NATO; MULTI-CAL is the receiver's marking |
| Trigger guard | IntegratedForged into the lower receiver |
| Safety selector | Radian Talon, ambidextrousBlack |
| Bolt release | Desert Tech proprietaryAmbidextrous |
| Magazine release | Desert Tech proprietaryAmbidextrous · standard on every Quattro-15 |
| Pivot pins | NitrideSOT standard |
| Sling mount | Integrated QD sling socketLeft side of the receiver |
| Tension screw | Upper receiver tensioning set screwDesert Tech's design · fit and feel, not accuracy |
| Trigger | LaRue Tactical MBT-2S, curved bowTwo-stage · straight bow shown, at no upcharge · the only trigger offered on the Quattro-15 series |
| Recoil system | VLTOR A5 receiver extension, A5H2 buffer, A5 rifle-length spring |
| Castle nut | Forward Controls Design CN5F, extendedMade for the VLTOR A5 system |
| Brace | SB Tactical SBA5®Black · on the VLTOR A5 receiver extension |
| Grip | B5 Systems Type 23 P-GripBlack · B5 Systems grip plug included |
| Sights | None standardOptional: Magpul MBUS 3 front & rear flip-up set (MAG1166-MAG1167), black · spring-loaded, ambidextrous push-button deploy · tool-less front elevation · rapid-select rear aperture · 0.44″ folded · +$75.00 |
| Magazine | Desert Tech QMAG-5353-round quad stack |
| Magwell adapter | Desert Tech Quattro-15 Magwell Adapter KitP/N ACC0292 · included · accepts standard USGI and AR-15/STANAG 30-round magazines |
| Case | 42″ Plano SE rifle case, blackEvery build ships in it · high-density molded polymer · high-density interlocking foam |
| Overall length | 30″ collapsed · 34″ extended |
| Weight, unloaded | 6 lb 7.6 oz |
| Finish | Black anodized upper, handguard and lower receiverBarrel and muzzle device Black Cerakote® · brace and grip black |
// Ordering
Trigger: LaRue MBT-2S, curved bow standard, straight bow at no upcharge. Ships with the A2 Extended Flash Hider (shown). Optional: 4-port hardened flash hider +$40 · Faxon MuzzLok® Gunner 3-port 5.56 steel brake +$60 · Faxon MuzzLok® stainless steel Plan B brake +$75. Ask about other choices: we offer a wide variety, including mounts for many suppressor manufacturers and other Plan B options.
Optional sights: Magpul MBUS 3 front & rear set (MAG1166-MAG1167), black, +$75.
Optional bolt carrier group, +$149: Young Manufacturing M16 Chrome BCG with HMB™ bolt (supplied as Young build it, without SOT's enhancements), or Microbest Super-Stake C158 all-chrome BCG, heavy-duty stake, with chrome HMB™ bolt.
Ships to your FFL dealer only.
Their capacity. Our architecture. One pistol.
The Quattro-15 lower and the QMAG-53 magazine are developed and manufactured by Desert Tech, and the receiver is rollmarked and serialised by them as the model of record. Second of Ten claims none of that engineering. What is ours is the pairing: an HM Defense Monobloc® upper on the Quattro-15 lower, which Desert Tech does not offer.
Fifty-three rounds, or any STANAG magazine
The pistol ships with one QMAG-53 and Desert Tech's Quattro-15 Magwell Adapter Kit (P/N ACC0292). The adapter lets the dedicated quad-stack Quattro-15 lower accept standard USGI and traditional AR-15 / STANAG pattern 30-round magazines, from a Magpul PMAG® to aluminum GI. No proprietary-magazine lock-in.
Where this pistol can ship
The Quattro-15 cannot be sold in California, Connecticut, Delaware, Illinois, Maryland, Massachusetts, New Jersey, New York, Rhode Island, Washington or Washington, D.C., under assault-weapon or feature-test restrictions, and the pistol cannot be sold in Hawaii. Colorado and Vermont restrict the 53-round QMAG-53; there, and wherever magazine-capacity limits apply, the pistol ships with compliant magazines instead, and the adapter is included regardless. Laws change: please confirm with your local FFL before ordering.
Mid-length gas at 12.5 inches
A 12.5-inch barrel normally forces a carbine-length gas system. HM Defense reaches mid-length gas on the 12.5-inch Monobloc® through precision port sizing, for a softer, less violent cycle in a short barrel.
Thermal fitted, with the gas block in the barrel
The Monobloc® barrel is thermal fitted to the MOD-0 forged upper, with no retaining compound and no bedding. Its gas block is milled straight into the barrel blank during manufacturing, so there is no separate block to clamp, pin or shift.
Suppressor-ready
Order the pistol with any of the Faxon MuzzLok® brakes (the Gunner 3-port or the stainless steel Plan B) and it is ready for a suppressor. The MuzzLok® indexes on its shoulder and removes cleanly, leaving the 1/2×28 thread for a direct-mount can.
The trigger: LaRue Tactical MBT-2S
The LaRue Tactical MBT-2S is the trigger on the Quattro-15 series: a two-stage trigger with a light take-up and a clean second stage, available with a curved or a straight bow. Second of Ten does not stone, polish or modify sear engagement surfaces.
Configuration shown
The pistol photographed carries the standard Black Cerakote® A2 Extended Flash Hider and the straight-bow trigger (the curved bow is standard, the straight bow at no upcharge). The 4-port and the two Faxon MuzzLok® brakes are optional, and other choices are available on inquiry, including mounts for many suppressor manufacturers and other Plan B options.
Ships in a hard case
Every Quattro-15 build ships in a 42″ black Plano SE rifle case: high-density molded polymer construction with high-density interlocking foam, so it arrives protected and you have a case for transport from day one.
Photographed as built
These are photographs of this pistol, not renderings, taken on both sides. Zoom in to read the rollmarks, machining and fit. The serial number is blurred.
Photography © Second of Ten LLC. MONOBLOC® and HMB™ are marks of HM Defense, LLC, used under license. Desert Tech, Quattro-15 and QMAG are marks of Desert Tech; SBA5® is a mark of SB Tactical; VLTOR of VLTOR Weapon Systems; CN5F of Forward Controls Design; B5 Systems of B5 Systems; Cerakote® is a mark of NIC Industries; MBT-2S of LaRue Tactical; Talon of Radian Weapons; WARHAMMER of Breek Arms; PMAG® and MBUS® of Magpul Industries; MuzzLok® of Faxon Firearms. Marks are the property of their owners; their appearance indicates that Second of Ten incorporates the component, not sponsorship, affiliation or endorsement.