Good afternoon everyone and welcome back to TFB’s Silencer Saturday brought to you by Yankee Hill Machine, manufacturers of the YHM Turbo K and YHM R9 suppressors. Last week we started our journey with the FN America M249S crew-served rifle in 5.56mm and 300BLK as a testing platform for suppressors that are rated for machine gun use. While we wait for the parts needed for the NFA “post sample” conversion, let’s talk about a feature of many modern silencers – the universal mount in 1.375 x 24. I find it is helpful to return to the basics for a deeper understanding of how our gear works. Let’s take a look.

• Thread Pitch: How I stopped worrying and learned to love M13.5x1LH
• SILENCER SATURDAY #12: Direct Thread Vs Quick Detach
• The More You Know: Thread Pattern Basics

SILENCER SATURDAY#252: The 1.375 x 24 Universal Mount EXPLAINED

Above (L to R): The Dead Air Primal 46, theSilencerCo Harvester EVO, The LMT AT ION 30, the PWS BDE, the YHM Turbo K, and the Prairie Tactical PTAC-30.

I had planned to finally finish the review of the Prairie Tactical PTAC-30 rifle suppressor, but it has been raining for 24 hours straight and the range is currently a lagoon. So stay tuned next week for the dramatic conclusion of our Prairie Tactical journey. Actually, there’s no drama – this silencer sounds great.

But as I like to preach from the suppressor pulpit, with today’s high performing cans, there is a lot more to consider than raw noise reduction.

Above (L to R): The SilencerCo Harvester EVO, The LMT AT ION 30, the PWS BDE, and the YHM Turbo K, all of which have universal mounting threads.

Case in point, one of my favorite 5.56mm suppressors is the YHM Turbo K because it is short, light, inexpensive AND it sounds great for its size. And I am not just saying this because YHM sponsors our Silencer Saturday series – many of our readers have reported similar results. But the one thing that YHM did with the Turbo K, R9, and Resonator lines that pushed me over the edge was the inclusion of the 1.375 x 24 (1 3/8 x 24) universal mount.

• YHM Nitro N20 (1 3/8 x 24 mounts)
• YHM Resonator K (1 3/8 x 24 mounts)
• YHM Turbo K (1 3/8 x 24 mounts)
• YHM Phantom QD Adapter 
• YHM Kurz QD Adapter

The YHM QD system is a relative veteran in the mount game and it performs very well as a one-handed quick attach/detach system that includes both flash hiders and muzzle brakes. It would have been easy to stick with a working product and hope that customers would change out all their other mounts for YHM muzzle attachments. But the evolution towards a universal mount system does two thing for manufacturers:

1. Allows owners of suppressors from different manufacturers to use your muzzle devices.
2. Allows owners of muzzle devices from different manufacturers to use your suppressors.

And that is pretty powerful, especially when you consider the price of three muzzle devices from some companies can add up to the price of a new suppressor.

Above (L to R) The YHM Turbo K, 1/2 x 28 direct thread adapter, the Dead Air KeyMo system and flash hider, the Dead Air Xeno system and brake, and the Q Cherry Bomb adapter and compensator. All of these are 1.375 x 24 compatible.

An Unofficial History of the 1.375 x 24 Universal Mount

As far as I can tell, SilencerCo was the original innovator of the 1.375 (1 3/8) x 24 adapter system on the Omega 300 suppressor which is now referred to as the Bravo System that includes direct thread mounts, QD systems like the ASR, as well as piston systems for titling-barrel pistol hosts.

• SilencerCo Bravo Accessories
• SilencerCo Omega 300 (Bravo Mount)
• SilencerCo Harvester EVO (Bravo Mount)
• SilencerCo Hybrid 46 (Bravo Mount)

Because the diameter of the mount (we’ll get to that in a second) is in the sweet spot for internal volume of the suppressor, increased hoop strength, and weight/material balance, other manufacturers took notice and used the opportunity to use the same threads specifications to capitalize on consumers loyalty to mounting systems. Dead Air brought their very popular KeyMo QD system from their Sandman suppressor  to 1.375 x 24 mount suppressors and the race to win the universal system battle was on. Griffin Armament  was also a front runner in the universal mounting system adoption and now has a compatible DUAL-LOK QD system as well.

• Dead Air Nomad (HUB)
• Dead Air Nomad Ti (HUB)
• Dead Air Primal (HUB)
• Dead Air Sierra (HUB)
• Wolverine PBS-1 HUB Adapter

Almost every manufacturer now offers universal mount compatibility for some of their suppressors. Almost. Some companies are very attached (see that?) to their QD systems and suppressors and are not ready to alter their designs to accommodate outside attachments. Not surprisingly, some of those companies have major government contracts and a design change would be detrimental to the product line.

Even the AB Suppressors Raptor – a reflex design – now feature 1.375 x 24 universal mount adapters. Below the AB Raptor is using the Dead Air Xeno system.

In the aftermarket world, companies like ECCO Machine are modifying suppressors for the 1.375 x 24 universal mount. I have seen some awesome examples “jailbroken” silencers that were locked into one QD system that had been threaded to use other manufacturer’s mounts.

Universal Thread Mounts – The Numbers

1.375 – Diameter of Threads in Inches

Looking at the below diagram can be slightly overwhelming. Forget major and minor diameters, the 1.375 or 1 3/8 value represents the diameter of the threaded portion in inches. You don’t need to do any math.

24 – Threads Per Inch

If the threaded portion of the mounting system was exactly one inch, there would be 24 threads total. It is a standard right hand twist (righty tighty, lefty loosey for those of you who may be slightly less handy around the house). And the threads on the silencer tube are female and the threads on the mounting system are male. I’d draw you a diagram of something going into something else, but I don’t want to make anyone blush.

Wrap Up

I probably took a very simple topic and gave you an overly complex explanation of things you will never need to know. However, it may help you make better decisions when you buy your next suppressor, or save you money by preventing you from buying a complete set of mounts and muzzle devices that don’t work with your suppressor. Yes, that was me.

Have a great week. Be safe, have fun, and we’ll see you back here next weekend for TFB’s Silencer Saturday.

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DEALERS: If you want your link to buy YHM suppressors included in future Silencer Saturday posts, email: silencers@thefirearmblog.com