LMT Monolithic Rail Platform



"Versatility at its best."

LMT Monolithic Rail Platform
By: Eugene Nielsen

Although the Lewis Machine and Tool (LMT) Monolithic Rail Platform® Defender isn’t the only AR with a monolithic upper assembly on the market, it is the only system that allows you to change barrels, calibers. The MRP® can even be switched from a direct impingement action to piston operation, or vice versa, in minutes while in the field, by simply removing two bolts from the receiver using a torque wrench and driver. This capability makes it a great choice for law enforcement agencies desiring maximum versatility.

The MRP is available in both rifle (MRP) and carbine (CQB) configurations. A variety of barrel types and lengths are available. The MRP can accommodate 14.5-inch, 16-inch and 18-inch barrels. The CQB can accommodate 10.5-inch, 14.5-inch, 16-inch and 18-inch barrels. 

In addition to 5.56 NATO, available calibers currently include .204 Ruger, 6.8mm SPC and 300 AAC Blackout /.300 Whisper. LMT has 5.45x39mm and 7.62x39mm in the final stages. Piston conversion kits are available in 5.56x45 (with 12-inch and 16-inch barrels) and 6.8 SPC (with 16-inch barrel). Additional barrels for the LM308MWS are available in .243 Winchester, .260 Remington, 6.5 Creedmoor, 7mm-08 Remington and .338 Federal.

The 300 AAC Blackout (300 BLK) is eliciting considerable interest in the tactical community.  According to Robert Silver of Advanced Armament Company (AAC), the round was developed when “a military customer wanted a way to be able to shoot .30-caliber bullets from an M4 platform while using normal bolts and magazines, and without losing the full 30-round capacity of standard magazines.” 

Full power 115- to 125-grain 300 BLK ammunition matches the ballistics of the 7.62x39mm.  Subsonic projectiles provide optimal performance with a suppressor. The 300 BLK ammunition with 220-grain Sierra OTM (open-tip match) bullet vastly outperforms the 9mm MP5-SD.

LMT also makes 7.62 NATO version of the MRP, the LM308MWS® Modular Weapon System®. Available in direct impingement (DI) only, a variant of the commercial LM308MWS has been adopted by the U.K. MoD as the L219A1 7.62x51 Sharpshooter rifle. The LM308MWS is first new infantry combat rifle to be issued in the U.K. in over 20 years.

LM8 Platform

In 2012, LMT added its LM8 platform to the lineup. LMT considers the LM8 platform as an evolutionary update on the monolithic rail platform. The LM8 is available in two rifle systems—the 5.56 mm LM8MRP and 7.62mm LM8MWS. The LM8 platform utilizes removable rail segments for a smaller, lighter system. The rail segments are available in four sizes to meet any mission. As with the MRP and LM308, you can change barrels and calibers and, in the case of the LM8MRP, switch from DI to piston.

LMT also makes two standard models. The LMT Defender Standard Model 16 and Defender Standard Patrol Model features a standard flattop upper receiver 16-inch chrome-lined 1:7-inch twist 5.56 barrel DI operation and standard M4 handguards. The Standard Model comes with Enhanced Gen 2 SOPMOD stock. The Standard Patrol Model comes with a standard M4 stock. If you don’t have a need to change barrels, calibers or want a piston system, the standard LMT models are an excellent option. You get the superb quality of an LMT carbine and save some money, as well.

We tested the LMT CQB MRP Defender Model 16 5.56. This CQB16 ships with a sling, operators manual, tactical adjustable rear sight, tactical front sight, 30-round magazine (10-round where required by law), two heavy-duty push-button sling swivels, torque wrench and driver, and three rail panels.

All LMT firearms are manufactured to Mil-Spec standards. All barrels and bolts are high-pressure tested and magnetic particle inspected. The carrier gas key and castle nut are properly staked. All LMT uppers and lowers are machined from 7075-T6 hardened aircraft grade aluminum forgings and anodized in a Mil-Spec Type III Class 2 hard coat finish. All steel parts are manganese phosphate finished (Parkerized).

Available in either select-fire or semi-auto, the MRP Defender 2000 lower features a NSWC Crane Mil-Spec LMT Second-Generation Enhanced SOPMOD buttstock on a six-position Mil-Spec extension tube, standard trigger group, ERGO grip and ERGO Gapper. The trigger pull is electronically tested and recorded. A LMT Enhanced Bolt Carrier Group and a two-stage trigger are available as options, as is an ambidextrous safety selector. A semi-auto bolt carrier group is employed on the semi-auto models.

The LMT SOPMOD stock was developed out of the needs of the US Special Operations community. The LMT Enhanced Generation 2 SOPMOD has a number of improvements over the original SOPMOD stock. It is constructed of a stronger fiberglass-reinforced polymer. The stock features two watertight compartments for storing batteries or spare parts, four sling attachment points including two color-matched stainless-steel QD swivel mounts, a sure-grip stock latch, and a padded butt-plate.

The MRP has a one-piece free-floating M1913 (Picatinny) quadrant rail system that eliminates 13 parts from traditional designs. Precision machined from a solid aluminum forging, the MRP completely replaces the upper receiver with a monolithic platform. The MRP upper features “T” marked rails to mark accessory locations so you know exactly where to re-install accessories after removal, which is especially important with optics and lasers. The CQB MRP comes with three LMT rail covers.         

The LMT Tactical Rear Sight and Tactical Front Sight are standard with the MRP. The front sight is adjustable for windage, elevation and peep adjustments. The rear sight is post adjustable for elevation. Front and rear sights are detachable without tools. LMT tactical sights permit instant transition from optics to irons. The LMT Tactical Rear Sight was selected by Crane for the CQBR / Mk 18 Mod 0 carbine fielded by Naval Special Warfare.

The MRP comes with LMT’s new Tactical Charging Handle. It features a newly designed tactical latch for easier manipulation of charging handle. The latch is large enough for ease of use, but not so large as to become a snagging hazard. The new design transfers all forces applied to the latch to the body of the handle and off of the roll pin, a source of weakness in standard AR charging handles.

The standard LMT MRP 5.56mm barrel is manufactured from cold hammer-forged machine-gun-grade chrome-moly vanadium steel. The barrel has a 1 in 7-inch RH twist with six lands and grooves. A military A2 flash hider is standard. The barrel and receiver have M4 feed ramps.

The barrel on the LMT DI systems has a low-profile gas block and a straight gas tube. The straight tube resists bending and provides better alignment with the carrier key. An angled gas port reduces barrel erosion for increased barrel life. The 16-inch barrel has a mid-length gas system. Shorter LMT barrels utilize a carbine-length gas system. The 16-inch barrels with a carbine-length gas system have a longer dwell time and are thus generally over-gassed, resulting in a sharper recoil impulse and increased wear on the parts over time.

We used Black Hills 5.56mm 77-grain OTM for functioning and accuracy testing. This is the commercial version of the 5.56mm Mk 262 Mod 1 ammunition that Black Hills is the sole source provider of to the U.S. military. Mk 262 Mod 1 ammunition has earned a well-deserved reputation for excellent accuracy and superior terminal performance, making it the preferred round of many SOF operators. Hard target penetration is slightly decreased with Mk 262 Mod 1 compared to M855.

Black Hills OTM ammo is loaded with the 77-grain Sierra MatchKing HP. It features Mil-Spec brass, sealed Mil-Spec primers, temperature-stable military propellent and is loaded to U.S. 5.56mm pressure limits. Velocity is 2750 FPS out of a 16-inch barrel. Five-shot groups from the standard 16-inch LMT chrome-lined barrel averaged 1.27 MOA. LMT’s stainless-steel match barrels are reportedly capable of sub-MOA accuracy.

While the rifle was kept well lubricated, it was not cleaned during my evaluation. Five hundred rounds were fired. There were no malfunctions. Standard GI magazines (with green anti-tilt followers) were employed. In summary, the LMT Monolithic Rail Platform takes Gene Stoner’s design to a new level. The LMT CQB Defender 16 5.56 we tested has an MSRP of $2,100.

Eugene Nielsen provides investigative and tactical consulting services and is a former officer. He may be reached at eugene.nielsen@live.com. 

Published in Law and Order, Jan 2014

Rating : 4.0

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not CHF barrel

Posted on : Mar 30 at 11:19 AM By pla748

are you sure the standard LM8MRP rifle has CHF chrome lined barrel? Nowhere mentioned the CHF barrel from LMT except your article.

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