OPS INC™ 3 Piece Collar Long for M4 (14.5″ Gordon Collar)

**All collars available as of 5/8/24 have a matte dark grey anodized finish. Future runs will have both black and grey anodizing available**

The OPS INC™ 3 piece collar, often referred to as the Gordon Collar, was designed originally for use with the issued M4 rifles of the 90s. It allowed the M4 suppressor to be installed on a 14.5″ barrel with carbine gas system. The clearance cuts on the bottom allow it to be used with an FSB and clear the bayonet lug, however an FSB is not required for use. The 3 piece M4 collar has since become an iconic part of many clone rifles of the era. You can learn more about historic builds here.

The 3 piece collar consists of an inner stainless steel sleeve and 2 outer anodized aluminum clamps. The sleeve is precisely fitted to the barrel and seats against the front of the gas block journal. The outer collar clamps tighten down to keep the assembly from moving.

Due to limited availability of M4 suppressors in the past, many people chose to clone rifles of the era with an AEM5 on a 12.7″ barrel using the longer collar. These days, we offer a shorter collar as an option that works with factory 12.5″ Car or 14.5″ Mid barrel. Those collars are available here.

Weight: 2.4oz (w/ “blank” sleeve)

Construction: Stainless steel sleeve, black oxide finish. 6061 aluminum clamps, type III hardcoat anodize. 8-32x.75″ Grade 8 cap screws with 9/64 hex drive.

**It is important that you read and understand the intricacies of fitting a 3 piece collar to your rifle! Read below for more details.**

Because of the application specific nature of the M4 suppressor and its original 3 piece collar, fitting it to modern barrels can be difficult and we highly recommend having it fit by a competent gunsmith. Generally speaking, it will work with most M4, SOCOM, and Government profile barrels without modification to the barrel. Some barrels however have gradual taper, oddly sized steps, or a flare at the end like many pencil barrels that may require some minor lathe work to correct. Historically, they were made for a specific barrel and were never meant to be a turn-key solution.

In order to offer as many mounting solutions as possible, we offer the 3 piece collar in two stocked versions, a long and short. If you are using an M4 suppressor on a 14.5″ carbine or 20″ rifle barrel, the long collar will be the appropriate choice. If you are using an AEM5 or other A-length, brake mount suppressor (ie. AEM5-30) on a 12.5″ Carbine barrel or 14.5″ Midlength barrel, you will need the short collar. B- length suppressors (AEM2, AEM3, AEM4) are not currently compatible with factory length barrels. If you need a sleeve for a 12.7″ barrel, please contact us.

For sleeves, most people choose the “blank” which allows it to be fitted to your specific barrel by a gunsmith. This will be the best option for most people due to varying barrel dimensions.

-Pre-fit instructions

**Please allow and extra 3-4 business days for processing pre-fit sleeves** All selectable sizes are typically stocked, however we may run out of a certain size due to demand.

If you have access to a micrometer and know how to use it effectively, we offer pre-sized sleeves available in .001″ increments. It is highly encouraged that you use a micrometer rather than calipers for measurement due to their ability to acquire a more precise measurement. To avoid abuse of this system, you will be responsible for return shipping charges if you measure incorrectly.

Sleeves are stocked in sizes from .719-.745″. If you need a size outside that range, contact us with your barrel information and we may be able to help you get one that fits.

Measure the diameter of the barrel immediately ahead of the gas journal. If your measurement is .748″ or larger, you are likely measuring the gas journal itself and need to double check. You also need to measure at least once more near the muzzle. If any point of the barrel is larger than the first measurement, your barrel may require gunsmithing. Taper or steps that are no more than .001″ larger than the first measurement are typically still useable. Some barrels have engraving or roll marks with high spots which may need to be removed with a stone or file. The pre-fit option comes with an additional  +.001″ and a -.001″ sleeve so you have some flexibility in fitment. If your measurement is in-between sizes, round up. While a snug fit is desired, the outer collar may compress even a .002-.003″ larger sleeve enough to prevent movement after installation.

-Outer Collar installation

After you have fitted your sleeve, it’s best to tighten the outer clamps with the suppressor snugged against the sleeve lightly. This allows the sleeve to seat all the way against the gas journal step. Be sure the clearance notch in the sleeve is aligned with the bayonet lug if applicable. Once snug, tighten the outer collar screws down leaving a small gap between it and the suppressor, .010-.020″ is sufficient. The suppressor should seat against the taper, not the outer collar. Use only enough torque as is necessary to retain the assembly with the suppressor removed, maximum of 35 in-lbs.