Just when you thought silencers couldn’t get any cooler…..along comes the tri lug adapter.
There’s no faster attachment method for a silencer than a tri lug adapter. You may have heard of it referred to as a 3 Lug adapter, or variations of these terms, but they all mean the same thing. 3-Lug is exactly what it sounds like; it has three lugs that protrude from the barrel that allow the attachment of silencers and other accessories.
How to Mount a Suppressor using a Tri Lug Mount
Depress the spring;
Quarter turn; and
That’s it. Now, you’re ready for some nice, quiet shooting. There are some things to consider when using 3-Lug, because, just like anything else, there are some pluses and minuses to the system.
If you're wanting a visual of installing a tri lug mount in action, our friend Alabama Arsenal created a video all about 9mm mounting solutions, and of course tri lugs were included in that!
Tri Lug Adapter History
Tri lug adapters were originally developed by Heckler and Koch for the quick attachment of accessories to the MP5. Interestingly enough, they originally weren't intended to be used with silencers. These 3-Lug mounts were originally added to the MP5 in 1966 for the quick attachment of a flash suppressor, blank firing adapter, or grenade launcher.
Actually, the first official MP5 Silencers were direct thread. The MP5 SD version had a very large silencer that threaded onto the back of the barrel, and the Navy version featured both 1/2x28 threads and 3-Lug; the way you see many guns with 3-Lug today, and the silencer issued with that attached to the threads.
It’s not known exactly when the first silencer was used with the 3-Lug adapter. However, an engineer named Tim Bixlar, who worked for Knights Armament and AWC patented the first 3-Lug adapter to be used with a silencer in the United States in 1988. It’s not clear if this was the first ever, but probably, the first in the United States.
Pros and Cons of the 3 Lug Adapter
That very unlikely history brought us to one of the most popular mounting systems for pistol caliber suppressors today. But, the 3 Lug adapter does come with some limitations and nuances that you need to consider before using it on your firearm. Typically, only a few companies actually use 3-Lug on their barrels; these are usually limited to Hk, Brugger and Thomet, and Noveske. You can buy a threaded adapter to allow your firearm to accept a tri lug mount, but that is an added cost. These 3 lug adapters can sometimes be rather expensive in relation to other adapters, but definitely worth it in the end.
In most cases your 3 lug adapter will thread into the back of your silencer. However, there have been a few silencers over the years with the tri lug as the permanent, and only attachment method built in the back of certain silencers. 3 lug is also limited to use with pistol calibers, and because of the design, the springs, and gaskets in the mechanism, it cannot take the heat generated from rifle calibers. You will also always want to make sure the spring in your adapter is fairly stiff. With extended use, these can wear out, and do need to be replaced from time to time. Tri lug works by the taper on the front of the lugs, aligning with a taper on the inside of the adapter. Then, the spring holds pressure on the taper and the back of the lugs as you rotate it on.
3 lug also can have some point of impact shift. What this means is, your point of impact on a target may vary slightly from your point of aim, depending on how the 3 lug adapter is oriented when you put it on your firearm. Basically, a tri lug adapter will never be useful for extreme accuracy or precision work.
There are a couple things to keep in mind when using tri lug adapter as well; always check your silencer to make sure the adapter is installed correctly, make sure you can’t pull the silencer off when installed, and while a little bit of play rotationally is pretty normal, you shouldn’t be able to rotate the suppressor very far at all. If you are using a 3 lug muzzle device over threads on your host firearm, you’ll always want to make sure that it is tight as well.
Here’s a quick recap of this section to show you the pros and cons of a tri lug adapter so you can see a side by side comparison and determine if this is the right mounting option for you!
It's important to understand where tri lug mounts shine, and why they might not be perfect for every situation. Luckily, there are a lot of mounting options out there for your 9mm needs, but 3 lugs deserve the spotlight sometimes too! There's no faster attachment method for a silencer, and as long as you keep a few considerations in mind, it works great!
This article was written by Alabama Arsenal. Follow and subscribe to his Instagram and YouTube for more information and drool-worthy images.
Good Article. What I would learn many years ago is that if the 3-lug Adaptor is not "timed" on the actual barrel so that one lug is in the 12 o'clock position, the POI/POA can be off the charts. I only figured it out after comparing my MP5K adaptor set-up to my HK94/MP5 with an original 3-lug barrel. Now that it's corrected it's fine. On my 3 MP5 gun/can combos I have the "best" position marked so that the cans are always oriented the same each time.