Home / Parts / Barrels / LMT® MRP™ Barrels / SOLGW Precision SPR 16″ 6mm Max®
// 6mm Max® · LMT® MRP™ compatible barrel
SOLGW Precision SPR 16″ 6mm Max®
16″ SOLGW Precision SPR barrel in 6mm Max®, converted for LMT® MRP™ upper receivers. 416R stainless, P3 polygonal rifling, intermediate-length gas with the block installed and pinned.
In stock · ships shooter ready
Price on request
- SKU BBL-6MAX-B160-MRP
- Caliber 6mm Max®
- Barrel length 16″
- Gas Intermediate
- Muzzle Thread protector
Ordered through the SOT Custom Shop — tell us your MRP™ upper and rail length and we’ll confirm fit before it ships.
// Specifications
The numbers
| Specification | Value |
|---|---|
| SOT SKU | BBL-6MAX-B160-MRP |
| Barrel maker | SOLGW |
| Caliber | 6mm Max® |
| Barrel length | 16″ |
| Material | 416R stainless |
| Profile | SPR |
| Twist rate | 1:7.5 |
| Rifling | SOLGW P3 polygonal, 3-groove |
| Bore | Unlined stainless |
| Finish | Black oxide |
| Gas system | Intermediate (13.65″ tube) |
| Gas block | Low-profile, nitride finish; installed and pinned with a stainless steel coiled spring pin |
| Gas journal | .750″ |
| Barrel interface | LMT® MRP™ upper receivers |
| Muzzle threads | 5/8×24 |
| Thread protector | SOT Standard Barrel Thread Protector, fitted — CNC-machined steel, black nitride finish |
| Muzzle device | None — fitted and timed to order |
| Bolt face | Standard 5.56 (.378) |
| Magazines | 6mm Max® magazines required |
| Inspection | Headspace gauged; bore and crown inspected; recorded on SOT-BIR-001 |
| Availability | In stock |
| Price | On request |
// About this barrel
Built, converted, gauged.
A precision six-millimeter barrel on a platform built for swapping. 416R stainless in the SOLGW Precision SPR contour, with SOLGW’s proprietary P3 polygonal three-groove rifling and a 1:7.5 twist — fast enough to stabilize the heavy end of the 6mm menu, which is the reason to be running six millimeters in the first place. 6mm Max® keeps the unmodified mil-spec .378 (5.56) bolt face, so changing barrels in your MRP™ upper does not mean changing bolt class.
SOLGW ladders gas length to barrel length across the Precision SPR range, and the 16″ takes the intermediate system on a 13.65″ tube — longer dwell and lower port pressure than a mid-length would give here, without asking a rifle-length system to work on a barrel too short to carry it. The shorter of the two lengths, and the easier one to carry.
The low-profile gas block is installed and pinned before shipment — port alignment verified, set screws torqued to specification, and a stainless steel coiled pin through block and barrel. Set screws clamp the block onto the journal; the pin stops rotation independent of clamping force.
Converted to the LMT® MRP™ barrel interface, then inspected, gauged and assembled by the Second of Ten build team to a documented standard. Installs with the MRP™ upper’s factory barrel hardware — no proprietary tooling and no permanent modification to the receiver. Headspace is gauged and recorded on the barrel inspection record before shipment.
Ships shooter ready: gas tube installed and the muzzle protected by the SOT Standard Barrel Thread Protector (CNC-machined steel, black or nitride finish), with no muzzle device fitted. Brakes, flash hiders and suppressor mounts are fitted and timed to order through the SOT Custom Shop. The protected bare thread is also the right configuration for a direct-thread suppressor. A headspaced bolt carrier group can be added and gauged to this barrel: SOT Enhanced Microbest C158 MPI DLC+, SOT Enhanced HM Defense in Black Nitride, or the SOT Enhanced Microbest Super-Stake with the Young Manufacturing HMB™ bolt.
At 16 inches this barrel builds a conventional rifle — no tax stamp, no registration and no wait. Requires 6mm Max® magazines.
// Includes
What ships
- 16″ SOLGW Precision SPR barrel, converted to the LMT® MRP™ interface
- Low-profile gas block, nitride finish, installed, aligned, torqued and pinned with a stainless steel coiled spring pin
- Gas tube sized to the gas system, black nitride finish, installed
- SOT Standard Barrel Thread Protector, fitted (CNC-machined steel, black nitride finish)
- Vacuum-sealed, with a Zerust® corrosion-inhibitor tube in the bore (remove before firing)
- Barrel inspection record (SOT-BIR-001)
// Options
Add to the build
- Headspaced bolt group: SOT Enhanced Microbest C158 MPI DLC+
- Headspaced bolt group: SOT Enhanced HM Defense, Black Nitride
- Headspaced bolt group: SOT Enhanced Microbest Super-Stake with Young Manufacturing HMB™
- Muzzle devices from other manufacturers, installed and timed — for a specific muzzle device, please ask before ordering
Every headspaced bolt group is gauged against this barrel and recorded with it.
// Matching headspaced bolt
Add a bolt, headspaced to this barrel
Any of these 5.56 NATO / 6mm Max® bolt face bolts can be added to this barrel. We gauge headspace with the bolt in this barrel and record the pairing on the barrel inspection record, so the two ship as a matched set.
| Bolt | Details | Price |
|---|---|---|
| Microbest C158 MPI bolt kit, chrome (phosphate extractor) | Bolt, extractor, firing pin, retaining pin and cam pin | $79.00 |
| HM Defense HMB™ bolt, black nitride | Cam pin socket in place of a through-hole | $135.00 |
| Young Manufacturing 5.56 M-16 bolt, black nitride | Item 1-50-12-301 | $89.95 |
| Young Manufacturing 5.56 M-16 bolt, chrome | Item 1-50-12-303 | $129.95 |
| Young Manufacturing 5.56 HMB™ bolt with cam pin, black nitride | Item 1-50-12-302 | $99.95 |
| Young Manufacturing 5.56 HMB™ bolt with cam pin, chrome | Item 1-50-12-300 | $149.95 |
Want a complete bolt carrier group instead? See the headspaced bolt groups under Options above, or ask the Custom Shop.
// Before you order
Fits LMT® MRP™ upper receivers only. Cut for LMT® MRP™-pattern upper receivers only — it will not fit a barrel-nut upper. Rail length governs clearance; tell us your receiver and rail and we will confirm fit before it ships.
16″ or longer. Not a short barrel under federal law, so short-barreled-rifle rules do not come into it. The firearm’s overall configuration is the purchaser’s responsibility.
WARNING: This product can expose you to chemicals including lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov.
Shipping. We do not ship barrel assemblies to California, Connecticut, Delaware, the District of Columbia, Hawaii, Illinois, Maryland, Massachusetts, New Jersey, New York, Rhode Island or Washington, or to Denver, Colorado, or Cook County/Chicago, Illinois. If you have questions, consult your local FFL.
Warranty. We warrant the conversion and the fit. A converted barrel is modified from its original configuration, so any coverage from the original manufacturer is at their discretion. If something goes wrong, come to us first.
// The rest of the range
Other LMT® MRP™ barrels
Monobloc® is a registered trademark of HM Defense. HMB™ is a mark of HM Defense, LLC, used under license. 6mm Max® is a registered trademark of BC Precision Ballistics. 6mm ARC is a trademark of Hornady Manufacturing Company. LMT® and MRP™ are marks of Lewis Machine & Tool Company. RIFLESPEED, SOLGW, Ballistic Advantage and Mos-Tek are marks of their owners. Second of Ten LLC is not affiliated with, sponsored by or endorsed by any company named here.