Ops Inc. 12th Model Style Silencers:
AEM5 & OCM5 - What You Need To Know
Ops Inc. suppressor visible on bottom. Brake and collar visible on top. Mk12 Mod 0 shown.
What makes an icon?
There are a handful of items in the firearm world identifiable by silhouette alone. The Kalashnikov pattern rifles with their distinctive curved magazines, the Thompson submachine gun with its forward vertical grip and drum, the timeless lines of the Colt 1873 Single Action Army, these are all instantly recognizable to even the most casual firearm fan. Discerning enthusiasts however, will be able to call out more selective outlines. A Heckler and Koch Mark 23 and Knight’s Armament silencer, the Franchi SPAS-12 shotgun, or the Charlie’s favorite, the Mk12 with an iconic reflex silencer. The Mk12 was equipped by the armorers at the Naval Surface Warfare Center in Crane, Indiana with an Ops Inc. 12th Model Suppressor. A reflex silencer is a design where the main body of the silencer telescopes back over the barrel to increase internal volume and affect the flow of combustion gasses while helping to keep down the total added length. This is part of what gives the Ops Inc. and the Mk12 such a unique profile.
US Marine taking aim with a Mk12 Mod 1 and silencer.
The Ops Inc. 12th Model is not just for Mk12 builds. It is also correct for the NSW RECCE/Seal Recon rifle and is just as at home on 12.5” variants of the legendary Gordon Carbine. What many haven’t thought of is how good these can look on other builds. Add one to an A1 style build and make your own mock Dissipator. Try mounting one under a rail to get that SD look without sacrificing barrel length. The performance leads many to use these silencers outside their traditional clone role. Today the 12th Model is manufactured by Allen Engineering (with Trajectory Arms) and Otter Creek Labs.
An AEM5 seen in TFB’s article about the Delta and Gordon Carbines.
Current Options - What’s the difference?
There are two models in the current market for an Ops Inc. style silencer. The original variant is the AEM5 from Allen Engineering. An alternative option is available from newcomer Otter Creek Labs. They each bring something different to the table for the discerning shooter and collector. Let’s compare the two. Both are full auto rated, dedicated 5.56 NATO units with a length of 8.8” and 1.5” diameter which use the original Ops Inc. mount system. The differences come with their materials and internal design.
Allen Engineering AEM5
100% Stainless Steel
21 oz.
Black finish.
Identical to the original military model.
Otter Creek Labs OCM5
Titanium and stainless steel.
16.02 oz.
Black or natural finish.
Newly designed baffle stack.
Cosmetically identical to the AEM5.
Mounts
Allen Engineering muzzle brake and long collar.
The Ops Inc. 12th Model attaches using a combination of a muzzle device and a collar mounted further back on the barrel. While the original mount was a muzzle brake, there are now different styles of brakes and flash hiders available. The 20 degree tapered collar provides the friction surface area to keep the silencer from backing off under rapid fire as well as making sure the unit is properly centered. Some of the mounts now on the market even eliminate the need for a separate collar and allow attachment to barrels previously too short for this type of silencer.
The Classic AEM5
Gunsnmammons reviews the Allen Engineering AEM5.
The history of the silencer can be found in more detail on The Firearm Blog. While Ops Inc. was who originally sold and got the contract for the 12th Model Suppressor, the vast majority of the units actually in circulation were made by Ron Allen. Now known as the AEM5, this iconic design remains in production today in its original form with exacting standards.
In 2022, a Utah based manufacturer named Trajectory Arms began production on the current generation of AEM5. Trajectory Arms is known throughout the industry for a high level of craftsmanship and expertise in the manufacture and tuning of AR pattern firearms with a focus on proper function during suppressed use. People all over the United States depend on weapons from the team at Trajectory. They bring this dedication and skill to carrying on the legacy of the AEM5 as it was originally built and still bearing the Allen Engineering markings. Ron is still heavily involved in the project and is ensuring all the attention to detail that makes the AEM5 special.
A New Challenger Approaches
The taper section visible on an Otter Creek Labs OCM5.
With its newly designed baffle stack, Otter Creek Labs claims the OCM5 is quieter and has less back pressure than the legacy design. The Firearm Blog details more about the OCM5 in Silencer Saturday #202. Solid performance and workmanship from a newcomer to the industry. It is excellent to have this option available to builders and shooters, especially those looking to lighten their rifles.
Suppressors
Allen Engineering AEM5
Ron Allen produced Sparks, NV units.
These are getting harder to acquire as Ron draws down production.
Trajectory Arms manufactured - Orem, UT 2022 Model
This is what is produced going forward.
Otter Creek Labs OCM5
Black Finish
Natural Titanium
Mounts & Accessories
Muzzle Brake and Collar Combos
Mk12 Mod 0/Mod H - Allen Engineering Brake and short collar combo.
Mod 1/NSW RECCE - Allen Engineering Brake and long collar combo.
Muzzle Brakes
Allen Engineering Ops Inc. 12th Model Muzzle Brake
Otter Creek Labs SPR Muzzle Brake
Flash Hiders
Otter Creek Labs SPR Flash Hider
Over The Barrel Mounts with Integrated Collars
Otter Creek Labs OTB Adapter
Otter Creek Labs OTB Muzzle Brake
Otter Creek Labs OTB Flash Hider
Collars
Allen Engineering #12 short collar. (Mk12 Mod 0 and Mod H)
Allen Engineering #12 long collar. (Mk12 Mod 1 and NSW RECCE)
Allen Engineering M4 collar.
Otter Creek Labs SPR long collar. (Mk12 Mod 1 and NSW RECCE)
Barrels
Potomac Armory 12.5” Gordon barrel with brake and collar.
Potomac Armory Douglas 18” SPR Mod 0/Mod 1 stainless.
With brake and collar.
Potomac Armory Douglas 16” SPR Mod H stainless.
With brake and collar.
Accessories
Allen Engineering Muzzle Brake Wrench
Allen Engineering Brake Thread Protector