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Muzzle Stand-off Device by Proof Mark

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Many years ago, guns were invented to – hopefully – put some distance between an attacker and oneself while combat ensues. The days of swords, rocks, truncheons, and other primitive contact weapons may be on the wane, FBI statistics still show more than half of law enforcement gunfights take place at distances of 0 to 5 feet.  And that can lead to a problem for handguns. In a close-proximity scuffle, a pistol’s slide can easily be pushed out of battery, preventing the all-important bullet to be launched at a particularly critical moment.


Proof Mark LLC, a veteran-owned firearm accessories design and manufacturing company, offers its solution to this problem: the Muzzle Stand-off Device (MSD) for the G19/23. The device is an accessory that prevents the slide from being pushed rearwards out of battery in contact fighting. It also has a hardened spike on its contact face for breaching and breaking glass.


The design intent originated in part with the Battle of Qala-i-Jangi, where a US Operational Detachment was practically overrun in combat that quickly turned hand-to-hand after all their ammunition was expended. They had to defend their position by literally beating down bad guys with empty guns. This inspired the meat tenderizer-looking striking surface, along with a nasty 17-4 stainless steel glass-breaker spike at its end that can come in handy when someone is trying to grab your piece in the clinch.

Around the same time, a government user group in Slovakia happened to share their experiences with Proof Mark LLC concerning several reports of Glock slides unlocking due to muzzle contact. The design lightbulb popped on, and a standoff device was sketched up. Even though it could have gone easily into production right then and there, Proof Mark LLC prides itself on being a company that thinks through and tests its designs to maturity before releasing them. Product development started in 2015, and variations have been wrung out in testing until the final design was ready for manufacturing and sale now in 2018.


While there have been standoff devices available prior to the MSD, the forethought and testing put into the MSD is unique in the industry. Anyone can make and bolt an L-shaped chunk of metal to a rail, but the Glock plastic frame (which has no stiffening glass fill) proves a challenge once you actually begin pulling triggers. The MSD was put through extensive testing which revealed two primary design obstacles: gas management at the muzzle and frame fitment.

Capturing excess gas behind any stand-off device generates a tremendous amount of force on the pistol’s dust cover that can lead to material fatigue. Which is a nice way of saying “it becomes a very effective muzzle brake on a gun not designed to have one mounted there, so you might crack your frame.” The Glock’s plastic dust cover/rail area isn’t made to handle forward “stretch” forces pulling on it. Proof Mark LLC overcame the first challenge of gas management by doing a lot of shooting and then incorporating that data into their carefully designed venting.

Proof Mark MSD inner

Another challenge was frame fitment (inconsistencies of Glock dust cover dimensions between generations, and even within a single generation, made universal attachment ability difficult.) For instance, the slides of the Gen5/19X’s are longer than prior generations, which led to a contouring of the back of the MSD to avoid interference. To overcome the differences between many generations of Glocks, a balance was struck between critical dimensions to achieve a good fit on everything through Gen3, 4, and 5’s. The MSD attaches to the frame rail with a Patent Pending 303 stainless locking block mechanism. It fits within the profile of the STANAG 4694 rail and offers toolless removal.


Prior to public release, the MSD went through a year of testing within one of the military’s special mission groups with positive feedback. Naturally, that feedback included a need to fit the Safariland family of holsters that SOCOM calls their standard (such as the 7TS G17/22 XC1 holster.)


Military use aside, Proofmark LLC’s President John Kennedy explained to us that this really finds its most useful purpose in mundane concealed carry: rocking a gun out of your holster while being grabbed, grappled with, or bear-hugged into can very easily put your pistol out of battery. The compact and lightweight MSD prevents this. Check the below video where Kennedy shows how easily just a small amount of rearward travel on the slide can prevent the gun from being fired.

The MSD is now available for the Glock 19, other models will follow.

Proof Mark website:


Instagram: @proof_mark

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