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Dimpling the receiver is a crucial step when building stamped receiver AKs to ensure reliability and longer parts lifespan. Without it, the firearm will ultimately end up damaging itself while firing and may end up destroying or significantly damaging core components such as the receiver requiring a full or partial rebuild.

Top Left: Conical Ram used for dimpling. Bottom Left: Dimpling Jig being used in a hydraulic press. Right: A properly dimpled 5.56/5.45 receiver.

Luckily, dimpling isn't that hard or intensive of a process. After drilling the holes for trunnions, you'll utilize a conical ram to press the receiver into the recesses present on the trunnions. Not every rivet hole needs to be dimpled, however, this does change from model to model, be sure to check your specs. If done right, the trunnion should essentially be mated to the receiver; preventing it from moving (excluding significant force) even without rivets.

Our Ops Manager Jeromy, shown here trying to pull the 1913 Trunnion out of the receiver after dimpling.

If the receiver is not dimpled, ultimately the forces from the firing cycle will beat the gun to death, requiring it to be rebuilt. This is more apparent on the rear trunnion as it will "walk" under recoil, sliding back & forth. This sliding eventually ends up shearing the rivet, or in some cases, the receiver being 'cut' by the rivet.

Once you start riveting the parts together, it's important to use swell neck rivets that will fill the dimpled recesses for the maximum amount of contact between the components, utilizing a non-swell rivet will end up shearing it while firing.

Don't mix them up: Non-Swell Rivet on the left & Swell Neck Rivet on the right.

Milled receivers such as the Sharps Bros. MB-47 or Arsenal SAM models, notably do not require dimpling as the trunnions are a part of the receiver itself. 

We'll summarize this with a direct quote from our Ops Manager Jeromy: " it make it strong  "

If you'd like to learn more about the finer details of building an AK, we cover all this and more during our AK build classes held through the year, click HERE for the full list. We've also stamped & milled receivers available on our site HERE.