Forget Threading: The 1960s Tech That Screws Today’s Better SMG and PCC Suppressor Mounts
Fact: Tri-Lug Barrels are the oldest, easiest, and one of the best ways to quickly mount a suppressor.
However, the attachment style is also limited in what it can do and, sadly, is overlooked.
Where did Tri-Lug or 3-Lug come from?
In Oberndorf, Germany, in the early 1960s, Helmut Baureuter, Manfred Guhring, Tilo Moller, and Georg Seidl cooked up probably the most mature sub gun of the 20th Century– the Heckler & Koch MP5. Recycling a roller-locked action first used on legendary machine guns in WWII and carried over to the G3 7.62 NATO battle rifle, it proved durable enough to become legendary.
It also had a funky, albeit innovative, barrel accessory mounting system on the muzzle: three equal-sized (roughly 0.310-inch) raised external lugs, spaced equally about 120 degrees apart center-to-center around the outside of the barrel, and ramped towards the muzzle.
These lugs were not an afterthought, welded, screwed, or pinned in, but something machined directly from, or forged with, the same piece of steel as the barrel.
Even back in 1966, when the HK MP5, developed from the HK54, was introduced with its slimline handguard and straight waffle-pattern 9mm magazines, it had a tri-lug barrel.
The tri-lug barrel endured through the Cold War and into the GWOT era and is still seen on classically styled MP5s and other SMG/PCCs.
The funny thing was that the tri-lug barrel wasn’t meant for attaching a suppressor. The lugs were originally for affixing accessories (Zubehör) such as a flash-hider (Feuerdampfer), a blank firing adapter (Manoverpatronengerat), and a sleeve for a 22mm cup-style tear gas grenade launcher (Granatfuhrung) fired with a blank round.
Thus:
Over the years, the accessories fell away while the MP5’s use with suppressors skyrocketed, especially after N (Navy) model MP5s entered the market in 1986, which included both a threaded barrel and tri-lug.
By 1988, inventor Timothy Bixler, with AWC Suppressors (Dr. Phil Dater’s old company) and Knights Armament, took out a patent (US4893426A) for a rotating collar utilizing Tri-Lug, and the rest is history.
How to use Tri-Lug
First off, Tri-Lug is a left-on (clockwise), right-off (counter-clockwise) kind of thing. Remember, “Left gets tight, right takes flight.”
Align the lugs, push in to depress the spring of the mount, twist about a quarter turn to the left until it passes the detents and stops, release the spring by letting go, boom. You are locked in. Reverse it to remove. Easy on, easy off, but still rock solid while in use.
Example:
Plus, with the Tri-Lug, you don’t have to worry about the suppressor backing off or loosening under rapid fire as you do with more common threaded-barrel models.
Tips:
- You can’t attach the can to the muzzle by twisting in the wrong direction, as the geometry won’t work, so don’t freak out about that.
- Also, new mounts and/or new barrels will likely be super tight, and the spring stout, so be sure to lube up and work them in on a safe firearm before heading to the range and trying it for the first time. Nobody gets confidence from the guy tugging on his can in the corner.
Not HK-only anymore
Besides assorted Heckler & Koch MP5/SP5 models and the myriad of clones such as the Century/MKE AP5 and SDS MAC-5, you have offerings from PSA like the AR-V and variants of the B&T APC9, GHM9, and SPC9 that sport in-spec Tri-Lug direct from the factory. Plus, you can get adapters from folks like SilencerCo that convert standard threaded muzzles to Tri-Lug.
As far as making your suppressor Tri-Lug ready, there are adapters for that as well from Banish, Dead Air, SilencerCo, and others, so that’s not a problem.
A new model to the market introduced earlier in the month is a dedicated Tri-Lug barrel version of the Kuna, a dependable roller-action that is fast becoming one of the most popular large-format 9mm pistols on the market.
MSRP for the unbraced model is set at $1,179, and the FSA-braced model’s MSRP is set at $1,330. Low-capacity 10-round options will also be available for those unfortunates living in restrictive states.
So, is Tri-Lug Perfect?
No.
As the design doesn’t support boosters (Nielsen devices), Tri-lug is tied to its original platform type: pistol caliber SMGs, PCCs, and large format pistols with fixed barrels. While primarily a 9mm offering, you also see Tri-Lug adapters for .45ACP (reverse to .578×28, 5/8×24, 9/16×24, and M16x1 LH threads), but that is about it. Plus, since the mounts are spring-based, they can wear out with extensive use, requiring new springs at some point in the distant future.
Still, for those classic MP5 styles and new offerings from folks like B&T and Springfield, the old standard can be a king when it comes to quick-detach.
