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Knight’s Armament XM-9, Snap-On Silencer

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This article originally appeared in RECOIL Issue 39

Pilots, Frogmen, and Spies

Back when The A-Team and Knight Rider were still must-see TV, Knight’s Armament was working on something a little different. The common name would be the Snap-On, but the official name when issued would be the XM-9. Ultimately, 3,800 KAC Snap-On cans were purchased by the U.S. Air Force for use for pilot escape and evasion kits in case they were downed in enemy territory, and also for Air Force Special Operations teams. An indeterminate number also went to the U.S. Army — and probably more than one clandestine service still has a handful in their inventory. While it’s no longer the latest and greatest in silencer technology, it still holds a special place both in our hearts and in history.


The majority of the Snap-On is dedicated to a gas expansion chamber.

The majority of the Snap-On is dedicated to a
gas expansion chamber.

The upgrade to the Frogman 1960s Hush Puppy, Snap-Ons were initially developed as a thread-on–type suppressor that we commonly see today. The second generation featured a locking gate-latch that was truly quick-attach when using a barrel machined specifically for this purpose. We’re told this taper pin mechanism was the baby of then-KAC engineer John Anderson.

Stacked sights definitely take some getting used to.

Stacked sights definitely take some getting used to.

The design of the Snap-On is fairly rudimentary by modern standards, but remember, we currently stand on the shoulders of giants. The majority of the silencer itself is dedicated to a large gas expansion chamber, and then the projectile runs through a series of polyurethane wipes and spacers. As each bullet passes through the wipe, the wipe seals gases behind it — at least until they wear out. We’ve seen many configurations of Snap-On wipes, from simple small apertures to crosscuts, to straight-up make-your-own-hole-with-a-bullet. Quite honestly, the latter works very well.

The wipe and spacer assembly consists of seven (or eight!) PU wipes with two separate spacers. Wipes are certainly consumable items, and their longevity depends on the ammunition used and the rate of fire achieved. While one could just disassemble the Snap-On and repack with wipes after they wear out, the design of the Snap-On allows you to just swap out the wipe and spacer assembly right in the field if need be.

We’re not entirely convinced it was a coincidence that the wipe size of the Gemtech Aurora, the successor to the Snap-On, shared the exact same dimensions. If you happen to own both, this is quite a boon. Let’s just say we were more than happy to discover this.

With supersonics, we were consistently high at 20 feet, and consistently right with subs. Neither grouped very well.

With supersonics, we were consistently high at 20 feet, and consistently right with subs. Neither grouped very well.

The dimensions of the Snap-On make it wide and squat, with a diameter bulging at 1.5 inches and sitting a hair below 5.5 inches in length. You’re not going to be able to utilize modern suppressor-height sights very well, let alone those on a stock 92F with the Snap-On mounted. But KAC had a solution: Mount the sights directly to the silencer.  The top of the rear gate-latch mechanism serves as a rear sight, and a simple bead is threaded in place for use as a front sight.

While this modified Beretta 92F wasn’t anywhere close to being the only pistol at the time equipped with a slide-lock, it’s probably among the last, if not the last. From our modern perspective, a slide-lock seems to only serve one purpose: to have a shot as quiet as possible — no action noise, no ejection port exhaust, no ejection port flame. However, they were initially developed for a different reason entirely.


The ambidextrous slide-lock is very easy to lock and unlock, even with gloved hands.

The ambidextrous slide-lock is very easy to lock and unlock, even with gloved hands.

Something that we take for granted with modern pistol silencers is the near universal use of a so-called Neilsen Device or muzzle booster. These recoil boosters were initially used on Vickers and Maxim machineguns in the early 20th century, but many years later found use in suppressed pistols. Since silencers add weight to the muzzle of a pistol, they can cause cycling malfunctions; a Neilsen Device temporarily uncouples the weight of the silencer when firing and allows for consistent, suppressed, semi-auto fire from a tilt-barrel action firearm. While the Beretta 92F doesn’t utilize such a mechanism, many other pistols do. A slide-lock allowed for a quiet shot, as well as ensuring cycling malfunctions weren’t present when using a silencer. Once Mickey Finn of Qual-A-Tec popularized the use of a Neilsen device with pistol suppressors, slide-locks went the way of the dinosaur.

In fact, in the early ’90s, when the U.S. Government was developing the Mk23 Offensive Handgun Weapon System (OHWS), the first solicitation required a slide-lock to be incorporated. However, with silencer technology improving at a rapid pace and recoil boosters becoming more common, the updated government solicitation removed the slide-lock requirement entirely.

RECP-181100-KACSILENT-locked back.jpg

At the Range
Knight’s Armament displayed their Snap-On with a box of Super Vel 147-grain subsonic 9mm, the ammunition for which it was intended. Not having any of that on hand, we opted to use both Israeli 158-grain subsonic and 165-grain Freedom Munitions subsonic for our purposes.

The accuracy was, hmm, rustic. What you have to keep in mind is that each projectile is passing through more than three-quarters of an inch of polyurethane before it exits the silencer. Coupled with the fact that the rear sight literally moves every time the silencer is mounted, and you get some fairly inconsistent shifts. But let’s be real here: This was never intended to be an Olympic target setup. Groups at 20 feet had significantly less shift than those at 30 but were still quite a bit to the right. Hey, this is one of the reasons wipe-only cans went out of style. That and the fact you can’t use any sort of hollow point or expanding ammunition, unless for some reason you want a guaranteed endcap strike.


When utilizing supersonic ammunition, which absolutely degrades the wipes much faster, we hit consistently high. Speaking of sights, we found the stacked sights to be rather optically confusing at first. When bringing the Beretta 92F equipped with a KAC Snap-On to bear, you’re presented with two totally distinct sight pictures — the standard (blocked by the can), and then the ones you’re supposed to use right on top.

The AAC version of the Snap-On was skinnier, but considerably longer than the original.

The AAC version of the Snap-On was skinnier, but considerably longer than the original.

What we were very pleasantly surprised with was the function of the slide-lock. As previously mentioned, the slide-lock allows for the quietest shot possible, because all action noise and ejection port exhaust is eliminated. After every shot with the slide-lock in place, it automatically dropped down from the slide and allowed for a very quick and efficient rack/eject/load. Some time was certainly spent with the design of this one.

Loose Rounds
In the year 2000, Advanced Armament Corp released their own version of the Snap-On. While it shared the same attachment mechanism, instead of a replaceable wipe pack, they rocked standard baffles. It was also considerably longer than the Knight’s version. Trade-offs with everything.

Below you see the contents of the entire kit, ammo and all.

Below you see the contents of the entire kit, ammo and all.

While the Knight’s Armament Snap-On is far from a modern-day pistol suppressor, it holds an important place in the history of silencer development. Looking back, you can’t help but feel like you’re looking at photos of yourself back in middle school; You can recognize yourself, but you dressed really awkwardly.

Knight’s broke out their old tooling (or maybe checked a dusty warehouse) and offered up 188 silencer/barrel combos for $1,999.95 each, and a mere 19
full kits as you see here for $8,684.12 a pop. Despite the Snap-On and Beretta slide-lock being dated, there are very few that wouldn’t be more than proud to have one in their collection.

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