The China Lake Model (or China Lake pump-action grenade launcher) is a pump-action grenade launcher that was developed by the Special Projects Division of the Naval Air Weapons Station (NAWS), which provided equipment to United States Navy SEALs.
The M79 and XM148 grenade launchers were single-shot, and the repeating T148E1 grenade launcher was unreliable, so a request was made to China Lake engineers. Navy SEAL teams were pleased with the resultant pump-action grenade launcher, since the tubular magazine held three 40x46mm grenades, and so with one grenade in the chamber, four grenades could be fired rapidly before reloading. In fact, a skilled operator could fire four aimed shots before the first one landed. The grenade launcher was extremely light for its size, since a significant portion of it was made of aluminium.
Submitted for field trials in Vietnam, this weapon apparently performed quite well with HE-Frag ammunition, but often choked on close-combat ammunition loaded with buckshot or flechettes (small arrows).
The pump-action grenade launcher features leaf iron sights similar to the M79. The front sight is a fixed square notch. Depending on if the leaf is folded or not, the rear square notch is either fixed or adjustable from 75 to 400 m in 25 m increments.
The larger screw on the left side of the receiver was designed originally for a quadrant sight to be mounted.
Though meant for SEAL teams, a handful were used by Marine Force Recon and Army 5th Special Forces Group.
Sources differ as to how many weapons were produced. One claims that between 20 and 30 were made. However, according to another source, only 16 were made. The highest original receiver number found is 50, but it may never have been made into a functional weapon. SEAL historian Kevin Dockery has confirmed 22 completed guns being carried on Navy records. Only three originals currently remain under US Navy control, the rest have since been demilitarized. It is sometimes mistakenly referred to as the "EX-41" or as the "China Lake NATIC". The EX-41 was a design prototype created in the mid-1990s based upon the earlier China Lake Model pump 40mm. The EX-41 was only produced as a single prototype. It was a follow up design created a two decades after the China Lake Model was produced. The China Lake NATIC designation is also erroneous as the weapon was never known by that designation. Since it was made on an ad hoc basis for special operations forces, it was not formally adopted and has no official military designation. Thus the SEALs referred to the experimental weapon by referencing the facility which produced it, thus creating the name, the "China Lake grenade launcher".
All four remaining original China Lake Model grenade launchers are on display in museums. Serial number 4, is at the UDT/ SEAL Museum in Fort Pierce, Florida while serial number 13, is on display in the War Remnants Museum in HCMC, Vietnam. Serial number 2 is stored at the US Navy Museum in Washington DC. One additional launcher is on limited display in a military restricted US Navy facility at NSWC Crane.
An effort to produce an improved version of the weapon began in 1992 when Samuel "Dutch" Hillenburg, a firearms writer specializing in military weapons, teamed up with master machinist Brian Fauci. In 2003, they achieved a breakthrough and were able to convince fellow writer and firearms enthusiast Captain Monty Mendenhall to finance their research effort. By 2004, they had a functional prototype and had formed Trident Enterprises Ltd. to continue their work on the project under government patent.
Brian Fauci later sold his military demonstration CSG/Trident China Lake Grenade Launchers to private parties when the contract cancelled for a Marine Corps replacement Grenade Launcher in Oct 2009. The very limited number of such prototypes improved upon the original China Lake launcher design were discarded completely by the U.S. military contract, with the U.S. Marine Corps selection of the M32 Grenade Launcher as its primary candidate as a replacement grenade launcher in 2009.
Starting in 2004 Brian Fauci's CSG of NY created China Lake reproduction launcher receivers, launcher serial numbers 1 through 8 separate of the ten contracted Trident launchers connected to the Airtronic deal. The CSG China Lake launchers have additional manufacturing to increase reliability of the China Lake Grenade Launcher cycling of action. CSG also replaced most flat headed screws to hex headed screws, the butt stock recoil pads are solid on the CSG launchers instead of ventilated as on the original China Lake launchers, no sling studs or swivels were installed initially on the CSG launchers.
Manufacturing Metals were upgraded with hardness treatment and improved metallurgy since the original China Lake development with both the Airtronic/Trident and CSG/Trident launchers. Total number of privately owned China Lake grenade launchers accounted for inside the United States is eight and additionally the four original China Lake grenade launchers from the Vietnam war remain in museums only.
In 2014 Samuel "Dutch" Hillenburg displays a CSG China Lake launcher in the TV reality series Sons of Guns in Season 5 Episode 5. The CSG/Trident launcher has a repair completed by Red Jacket Firearms by a CNC manufactured replacement wing lock. Joe Meaux completes the replacement part using the CNC after hundreds of rounds had been fired through the launcher causing the wing lock to shear.
In June 2007, China Lake launchers were in limited production by two different companies and were ready to market under contract the reproduction launchers to the U.S. military by way of defense contracts. At that time, the U.S. Military was approached with an offer from Airtronic USA (then the current government manufacturer of the M203 after Colt) to acquire a license for military production and sales. Both CSG and Airtronic/Trident launchers were considered for replacement of the M79 stand alone launcher in the Marine Corps.
In July 2007, Airtronic USA announced that they were entering large scale production with an initial order for 500 units destined for US military forces. This announcement occurred simultaneously with a demonstration of the CSG/Trident China Lake launcher in an episode of the popular military technology program, "Weaponology". As of 2009, Airtronic USA will commence manufacturing the launcher in its original form and another variant with picatinny rails, pistol grip and retractable "M4 Carbine" type stock.
From 2007-2009 contractor and manufacturer Airtronic invested over two million dollars with Trident company a contract to reproduce the China Lake Launcher original design and also to advance further development of the original design incorporating a M203 handguard, M4 style collapsible stock and barrel incorporated with a top rail for accessories and extend the magazine tube to allow four grenades plus one in chamber.
Airtronic/Trident China Lake Grenade Launcher displayed on link. 
Ten of the China Lake Mil-Spec Reproduction launchers were manufactured in 2009 but eventually the two companies involved (Airtronic and Trident) parted ways after legal action. During the legal actions of courts the U.S.M.C adopted the Milkor M32 Grenade Launcher as a replacement. 
An Original 1967-1969 China Lake grenade launcher none are known under private ownerships. Trident/CSG China Lake Grenade Launchers from the 2009 defense contracts are the last eight known legal launchers to be in private hands and are valued within the $70K TO $75K USD based on past auctions. One of the eight CSG/Trident launchers will be selling at RIA auction house in the late summer of 2019. All Airtronic/Trident launchers were destroyed. No other official Mil-Spec manufactures are known with a government patented contract since 2009. CSG/Trident China Lake launchers are considered the rarest NFA grenade launchers on the market and are transferable in the U.S.A. as a form one or four NFA weapon.
All CSG/Trident China Lake Grenade Launchers remaining in registry can be considered of extreme rarity and will eventually be considered relics of military interest. Note: Filed Sept. 1, 1967 Alfred F. Kermode holding patent 3,435,549 PUMP TYPE TUBULAR MAGAZINE REPEATING FIREARM was transferred to and held with the U.S. Gov and Filed under April 1, 1969 to the U.S. Patent office. No other China Lake reproductions are allowed unless approved by the U.S. Government for direct defense contract to the U.S. Government. V. C. Muller Attorney. U.S. Patent Office.