Witness Marks on Shotguns

Aridus Industry is an awesome company. I’m not just saying it because they make shotgun stuff, and I love shotguns. They are a small shop that is making innovative accessories for the shotgun market. Aridus Industries really helped the Beretta 1301 become the shotgun it is today. I follow them on social media, and they recently posted a photo of a shotgun covered in Witness marks and remarking that serious-use shotguns should have witness marks. Aridus Industries is right, but I figured I’d take the time to elaborate on the what and why of witness marks.

The What and Why of A Witness Mark

A witness mark, also called an index mark, is a small, visible marking used to help track the attachment of accessories. Specifically, it allows you to track accessories that are threaded onto the gun. Shotguns are heavy, recoiling, violent weapons that are always moving around. That movement makes things unthread and loosen and eventually come off or create malfunctions.

I first experienced this with a magazine tube extension, and they are common fodder for the problem. It’s not like the tube popped off, but my 930 started having failures. It was only when I realized the shells could move without resistance that I noticed the tube was just loose enough to create slack. It’s not always obvious.

Witness marks are placed on the threaded device, be it a mag tube nut or bolt for a mini red dot, and at the base, it’s attached. It’s one continuous mark. This way, when something rotates or loosens, it’s immediately obvious. You can easily see when the bolt is working its way out of your red dot or when the tube extension is starting to come off.

Where Should You Witness Mark a Shotgun?

Everywhere! Really, on anything that’s threaded onto your shotgun. This includes sights, optic rails, optics, magazine extensions, bolt release extensions, and beyond. If it has threads, a small witness mark finds a spot. I use a Birchwood Casey paint pen, and I don’t go too overboard with the entire thing. It’s just a mark big enough to see.

Let it dry, and occasionally give them a peek. It becomes obvious when they move. You’ll have to update them every so often because paint pens tend to wear away. Maybe one day, I’ll have them laser engraved, but for now, a paint pen works.

Put them everywhere and check them often. If you run a shotgun hard, you’ll be surprised at how quickly things can get loose.

Travis Pike
Travis Pike is a former Marine Machine gunner who served with 2nd Bn 2nd Marines for 5 years. He deployed in 2009 to Afghanistan and again in 2011 with the 22nd MEU(SOC) during a record setting 11 months at sea. He’s trained with the Romanian Army, the Spanish Marines, the Emirate Marines and the Afghan National Army. He serves as an NRA certified pistol instructor and teaches concealed carry classes.