SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

Good afternoon everyone and welcome back to TFB’s Silencer Saturday brought to you by Yankee Hill Machine, manufacturers of the very capable YHM Turbo K suppressor. Last week we took our first look at the Dead Air Sierra-5 5.56 suppressor. This week we embark on our journey into the world of Knight’s Armament signature reduction devices with a look at the KAC mounts for 5.56 and 7.62 rifles. Let’s take a look.

KAC @ TFB


PEW Science Sound Signature Review – KAC QDSS-NT4

  • Check out the latest PEW Science review on the KAC QDSS-NT4.
PEW Science Sound Signature Review - KAC QDSS-NT4

PEW Science Sound Signature Review – KAC QDSS-NT4

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

I have spent the last few months (and a small fortune) collecting examples of every Knight’s Armament rifle suppressor and muzzle device available. In some cases this required scouring FFLs looking for old stock sitting on a shelf, buying used pieces on the second-hand market, or paying well over MSRP to gather all the required KAC equipment for a series of reviews. Instead of setting up a gofundme for “scientific sound testing equipment”, I’ll probably need to sell off the majority of my Knight’s signature reduction devices to fund future reviews – I have transferable-level money tied up in KAC gear. And not MAC-10 transferable money either.

One of the reasons I was obsessed with finding KAC silencers is that I felt that I had neglected a large section of the history of modern suppressor development. After four years of Silencer Saturday editions, I felt a little guilty that I hadn’t featured silencers like the KAC-NT4 which undoubtedly changed the way everyone, military and civilians alike, viewed rifle suppressors. And how could I have waited so long to discuss the KAC QDC mounting system; it could be one of the slickest designs ever made. Long story made short, I am trying to make up for lost time.

I am not an expert on Knight’s Armament firearm development, so I posted some questions for my friends over at AR15.com. Luckily I had expert responses that shed some light on the early days of the QDSS-NT4 development.

  • The original MIL requirement called for seven 30 round magazines, fired as fast as possible.
  • The first versions of the QDSS suppressor did not have the now iconic corncob girdle wrapped around the body of the suppressor
  • The first version passed with seven 30 round magazines using M193 but failed on the last magazine when using M855.
  • One of the early versions used a 3/4 corncob girdle and a different latch locking mechanism.
  • The full corncob girdle KAC NT4 was the only manufacturer that passed the seven magazine test.
  • The QDSS NT4 was the only manufacturer that the later SOCOM standard at the time.
  • The full model name is NT QDSS M4 with ‘NT4’ being the shortened designation.
  • NT stands for New Technology.
  • QDSS stands for Quick Detach Sound Suppressor
  • Early versions did not have the retaining ring that kept the latch plate in place.

An early version of the KAC QDSS (right) – Credit: User ‘Coldblue’ on AR15.com

The QDSS-NT4 is the only centerfire rifle suppressor that I have seen that can be shot using water as an ablative material. Also, I found the emergency removal and quenching sections in the operators manual to be interesting. Note, dunking a super hot suppressor in water while mounted and the bolt open could spray boiling water out of the action.

Also note that when using the emergency removal procedure, the rifle should be inverted and the suppressor pointed at the enemy while firing a single round with the latch plate open.

KAC QDSS-NT4 Operators Manual

KAC QDSS-NT4 Operators Manual

Let’s take a look at the mounts and muzzle devices.

Details and Specifications:


Knight’s Armament QDSS-NT4 Suppressor 

KAC M4QD Flash Hider Kit: 

KAC NT-4 MAMS:

KAC 5.56 Shim Kit: 

The KAC QDSS-NT4 Latch Plate and Retaining Ring

The NT4 mounting system is comprised of a mating/docking area where either the M4QD or MAMS muzzle device slides in, a latch plate that slides into place in the groove of the muzzle device, and a retaining ring that will prevent the latch from moving.

Below, the NT4 with latch plate closed (down position) and the retaining ring (tab at the 9 o’clock position) disengaged.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

Below, the NT4 with latch plate open (up position), the retaining ring (tab at the 9 o’clock position) disengaged, and the M4QD flash hider in the docking area.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

KAC QDSS-NT4 Operators Manual

Below, the NT4 with latch plate closed (down position), the retaining ring (tab at the 9 o’clock position) disengaged, and the M4QD flash hider in the docking area.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

Below, the NT4 with latch plate closed (down position), the retaining ring (tab at the 2 o’clock position) engaged, and the M4QD flash hider in the docking area.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

KAC QDSS-NT4 Operators Manual

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

Here’s a close up look at the QDSS MAMS muzzle device.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

The KAC 7.62 Quick Disconnect Coupling (QDC) Suppressor

KAC 7.62 QDC Suppressor (legacy)

  • PN; 30178
  • Weight: 19.6 oz
  • Length: 7.787″

KAC 7.62 QDC Flash Suppressor Kit (1/2 x 28 muzzle device for 7.62 QDC Suppressors)

The original QDC suppressors had a flat front without the flash hider tines found on the current QDC models.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

Looking down through the QDC 7.62 at the blast baffle.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

The 7.62 QDC can be used on 5.56 hosts with a closed tine flash hider in a 1/2 x 28 thread pitch.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

The KAC 5.56 QDC/CQB Suppressor

KAC 5.56 QDC/CQB Suppressor

KAC 5.56mm QDC Suppressor

KAC 5.56 QDC 3-Prong Flash Eliminator Kit

Manufacturer’s Page: https://www.knightarmco.com/12813/shop/signature-reduction/muzzle-devices/12-28/556mm-qdc-flash-eliminator-kit

  • Weight: 2.3oz (65g)
  • Length: 2.15″ (53mm)
  • MSRP: $123.75

KAC 5.56 QDC MAMS Kit

KAC SR-15 11.5” CQB MOD 2 Upper Receiver

The KAC 5.56 MAMS (Multi-Axis Muzzle Stability) Brake has been engineered to increase controllability, to significantly reduce felt recoil, and to help mitigate a rifle’s flash signature as compared to traditional muzzle brake designs. The MAMS is a neutral bias brake that combats both muzzle rise and drift upon firing. Depending on the gun’s barrel length, it can reduce felt recoil in a 5.56x45mm gun by as much as 67 percent.

The 5.56 QDC MAMS has three short tines to mitigate flash.

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

The KAC MAMS could have an entire post to itself. Multi Axis refers to the angled porting in the brake that counteracts muzzle rise and recoil.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

The majority of the porting is drilled at an approximate 15 degree angle back towards the rifle. Two rows of ports near the mounting surface and four ports at the 12 o’clock position near the muzzle are drilled at a 90 degree angle.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

The 5.56 QDC Flash Eliminator comes standard on all 5.56mm upper receiver groups and carbines/rifles. An index pin is timed at the 12 o’clock position on all QDC mounts.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

Below, the QDC collar is fully opened, allowing the seven mounting bearings float freely.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

Below, the 5.56 QDC MAMS is sitting in the docking area with the collar fully opened. The index pin lines up the bearings on the suppressor with the corresponding divots in the 5.56 QDC MAMS.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

Below, the 5.56 QDC MAMS is sitting in the docking area with the collar fully closed. A full turn counterclockwise seats the bearings firmly in the divots on the MAMS.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

Below, the 11.5” SR-15 CQB with the 5.56 QDC/CQB fully engaged.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

The current KAC QDC suppressors have tines to mitigate flash. I’m really looking forward to seeing the new Pressure Reducing Technology QDC models that should hit the market later this year.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

NO GO: Here’s a look at the 5.56 QDC MAMS in the 7.62 QDC suppressor. It is way too small to mount up. That’s what she said.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

Size does matter. Check out how much bigger the 7.62 QDC MAMS is compared to the 5.56 QDC MAMS. You can also see the angled ports a little better and the difference in port patterns.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

The 7.62 QDC mount uses nine bearings to secure the suppressor to the muzzle device.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

Below: On the left is the 5.56 QDC/CQB, on the right is the 7.62 QDC.

SILENCER SATURDAY #232: KAC Mounts - KAC QDSS and KAC QDC

SILENCER SATURDAY #232: KAC Mounts – KAC QDSS and KAC QDC

I just came in from putting a few mags through the NT4 on full auto. We’ll save the rest of that story for next week.

Be safe, have fun, and we’ll see you back here next weekend for another Silencer Saturday.


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