16″ 5.56 NATO Quattro-15 Monobloc® A5 Rifle
13″ Picatinny quad rail · chrome-lined or standard bore · VLTOR A5 · B5 Systems furniture · black
16″ 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 a 13″ SOT Wedge-Lock Picatinny quad rail handguard, paired with a Desert Tech Quattro-15 lower receiver with a Radian Talon ambidextrous selector, a LaRue Tactical MBT-2S trigger, a VLTOR A5 receiver extension with an A5H2 buffer, a B5 Systems Enhanced SOPMOD stock and Type 23 grip in black, and a Desert Tech QMAG-53 quad-stack magazine. Upper, handguard and lower black anodized.
// Specification
| Model | 16″ 5.56 NATO Quattro-15 Monobloc® A5 Rifle13″ Picatinny quad rail · SKU QTR15-MB-B160-H130Q-BLK-R-A5 (standard bore) · QTR15-MB-B160CL-H130Q-BLK-R-A5 (chrome-lined) · proposed |
|---|---|
| Series | Quattro-15 · Direct impingement (DI)Rifle, Title I |
| Chambering | 5.56×45mm NATO.223 Remington compatible |
| Barrel | 16″ HM Defense Monobloc®, chrome-lined or standard boreChosen at order · 4150 chrome-moly steel (CrMo) · balanced taper profile · Black Cerakote® |
| Twist | 1:8 |
| Muzzle thread | 1/2×28 |
| Gas system | Mid-lengthGas 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 | 13″ SOT Wedge-Lock Picatinny quad rail, black anodized15″ or 13″ M-LOK, or 13″ Picatinny quad rail, chosen at order · free float · twin-lug wedge lock to a steel barrel nut, anti-rotation tabs |
| 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 rifle 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 available · the only trigger offered on the Quattro-15 series |
| Recoil system | VLTOR A5 receiver extension, A5H2 buffer, A5 rifle-length spring |
| Stock | B5 Systems Enhanced SOPMODBlack |
| 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 | 34.5″ stock collapsed · 38″ extendedSame with all three handguards |
| Weight, unloaded | 7 lb 9.9 ozWith the 13″ Picatinny quad rail |
| Finish | Black anodized upper, handguard and lower receiverBarrel and muzzle device Black Cerakote® · B5 Systems furniture in black · offered in black only |
// Ordering
Standard bore $2,100.00 · chrome-lined bore $2,299.00 · the same price with any of the three handguards.
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 rifle.
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 rifle 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 rifle 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. Colorado and Vermont do not restrict the rifle itself but do restrict the 53-round QMAG-53; there, and wherever magazine-capacity limits apply, the rifle ships with compliant magazines instead, and the adapter is included regardless. Laws change: please confirm with your local FFL before ordering.
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 rifle 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.
Choose the handguard and the bore
The A5 rifle is one rifle with two choices at order: a 15-inch or 13-inch SOT Wedge-Lock M-LOK handguard or the 13-inch SOT Wedge-Lock Picatinny quad rail, and a chrome-lined bore ($2,299.00) or a standard bore ($2,100.00). Everything else is the same build.
Configuration shown
The rifle photographed carries the standard Black Cerakote® A2 Extended Flash Hider. 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 rifle, 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; VLTOR of VLTOR Weapon Systems; 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.