GRIFFIN ADJUSTABLE AR-15 GAS BLOCK (.750″)

NOTE: This gas block requires the use of a straight gas tube, click here to purchase one. 

It has long been our belief that the ideal AR-15 should have 2 simple modes – Normal and Suppressed – affording a K.I.S.S. concept optimization for use with and without suppressors, easily adjustable by means of the tip of a live round of 5.56mm ammunition. The Griffin Adjustable AR-15 Gas Block achieves this simplicity and is a product made possible by the acquisition of two patents from MicroMoa LLC – the original manufacturers of the “Govnah gas block”.

The Griffin Adjustable AR-15 Gas Block provides normal and suppressed operation via rotationally sliding a regulator plate from the Normal position to the Suppressed position. This regulator plate is detented via a 718 inconel spring and ceramic ball bearing ensuring material strength under extreme operating temperatures. There are two 180° opposed sides of the regulator plate, each affording a normal and suppressed setting (Refer to the spreadsheet covering regulator hole sizes). One side of the block is identifiable by two grooves cut on the side of the selector cutout. This allows a shooter to find the side of the disk that works best for an application, and if that is the grooved side, a paint pen can be used to make a vertical mark on the right side of the rail, allowing the end user to know the grooved side is on the right (laser marked side of the block) when that build is used. Once this initial setup has been determined, a one-click operation configures the rifle from normal to suppressed modes of operation. An L could also be marked to distinguish which rifles have low back pressure suppressor regulator plates, from those using conventional regulator plates.

The suppressed gas ports on conventional plates are .004″ apart offering two sizes, and the low back pressure plates have 2 sizes .008″ apart with the exception of the .300BLK plate.

Note: The .300BLK low back pressure plates have to be set to normal to allow rifles to function with subsonic ammunition and a suppressor. The use of a low back pressure suppressor with a .300BLK AR-15 will likely be incompatible with semi-automatic function of the rifle with subsonic ammunition, as most guns are tuned to run subsonic only when a conventional back pressure suppressor is affixed to the muzzle of the barrel.

Griffin to-date has developed a total of 9 plates to address the vast majority of setups in the hands of end users today. Additionally, we offer 2 pre-drilled “Drill Your Own” plates with .033″ starting holes to reduce drill breakage, that allow the user to determine and drill their preferred hole sizes for their desired results. One of the pre-drilled options has the two .096″ normal (unsuppressed) operation holes pre-drilled, and the other has all four holes spot-chamfered to .108″ with .033″ pre-drilled starter holes only, allowing end users to customize all four port sizes. Which plate you should use is a factor of your host firearm’s gas system length, its caliber, and the type of suppressor being used (conventional or low back pressure/high flow).

Don’t know which regulator plate to pick? Our knowledgeable CS team is standing by and will be happy to guide you through choosing the proper regulator plate for your setup. Click Here to contact Customer Service.

Conventional Suppressors vs. Low Back Pressure Suppressors

Conventional suppressors can be defined as suppressors that don’t have printed channels or printed gas bypass features to increase gas evacuation speed. Low Back Pressure suppressors are hallmarked by extensive baffle-to-baffle porting, complex internal geometries, and vented end caps. Conventional suppressors are designed to offer higher muzzle sound suppression, and often are made using numerous stamped or CNC-manufactured components. They typically are not printed, although a more conventionally performing suppressor can also be printed. Ejection patterns are another way to identify low back pressure suppressors. Typically, conventional suppressors change the ejection pattern of an AR-15 from 4:30 to around 1-2 o-clock, whereas low back pressure suppressors have less effect to alter spent case ejection patterns from unsuppressed normal operation.

Griffin Suppressor Recommendations: All Griffin Suppressors except the Optimus® 6 & 7 should utilize the “Conventional” plates. Optimus® 6 & 7 Suppressors should be paired with a “Low Back Pressure” plate.

Available Regulator Plates

You can purchase standalone regulator plates here. Each plate is discretely numbered via a laser-mark on the diameter of the regulator disc. Take note of this number, if contacting customer service, so they know which plate you have.

• Rifle-Length Gas System | 5.56mm | Conventional Suppressor
• Rifle-Length Gas System | 5.56mm | Low Back Pressure Suppressor
• Mid-Length Gas System | 5.56mm | Conventional Suppressor
• Mid-Length Gas System | 5.56mm | Low Back Pressure Suppressor
• Carbine-Length Gas System | 5.56mm | Conventional Suppressor
• Carbine-Length Gas System | 5.56mm | Low Back Pressure Suppressor
• Pistol-Length Gas System | 5.56mm | Conventional Suppressor
• Pistol-Length Gas System | 5.56mm | Low Back Pressure Suppressor
• Pistol-Length Gas System | .300 BLK | Conventional Suppressor (This has the same dimensions as the Carbine-Length | 5.56mm | Conventional Suppressor regulator plate, and are thus the same product)
• Pistol-Length Gas System | .300 BLK | Low Back Pressure Suppressor

• Drill Your Own (4x Holes – All .033″ diameter for subsequent drilling to final size)
• Drill Your Own (2x .033″ Holes for subsequent drilling to final suppressed size | 2x .096″ Holes for normal/unsuppressed use)

Drill Your Own DISCLAIMER: This operation should be performed by a professional gunsmith with a high-level understanding of AR-15 gassing and proper port sizes. Customers purchasing a Drill Your Own Plate assume all responsibility for the performance of that product once it has been altered. Griffin is not responsible for improperly drilled plates for any reason, and will not accept returns or exchanges on these items. We recommend securing the plate in a vise with the U shaped notches for bullet tip adjustment in contact with each jaw of the vise.  We recommend using high speed steel or cobalt drill bits held on axis of the pre-drilled holes, with oil coolant, and slow drill RPMS with light pressure, to ensure positive results.  

Features

• User’s Choice of 17-4, H900 heat treated regulator Plate, affording 3 Effective Positions with 2 Quick-Change Settings per 180 degree side of the plate.
• Heat treated, barrel quality 416R Stainless Steel Construction
• Black Oxide Finish
• .750″ Gas Block Diameter with mil-spec tolerances of gas tube and barrel holes
• Low Profile Design – Fits Under Most Rails
• Gas block Spline Pin – Included- optional and requires 1/8″ drilling of barrel in assembly for use
• Knurl Grip, Cup-Pointed Fasteners at .460 hole spacing – Included
• Gas Tube Roll Pin – Included
• Pre-drilled for ease of barrel pin installation – hole can be used as a guide for drilling barrel in assembly. Bridgeport or similar mill recommended.

Digital Manual

• Click Here to view the digital manual for the Adjustable Gas Block

INSTALLATION DISCLAIMER: The installation should be performed by a professional gunsmith with a high-level understanding of AR-15’s and familiarity with the use of a Bridgeport or similar milling machine and reasonable skill as a machinist. Griffin is not responsible for damage to firearms caused by poorly skilled and improper modification to firearms. The use of this gas block requires the use of a straight gas tube. Click Here to purchase a straight gas tube on our website. 

Additional information