HM Defense HMB Bolt Carrier Group – Black Nitride

5.00 out of 5
(1 customer review)
sku: HMB-BCG


In stock

In stock


The HM Defense HMB Bolt Carrier Group – Black Nitride corrects a natural weak point in existing Mil-Spec M16, AR-10 & AR-15 bolts, where the cam pin hole passes through the bolt.

Under extensive use, including the stress of combat, a standard Mil-Spec bolt can fail at the cam pin hole location. The HMB Bolt by HM Defense eliminates the pass-through cam pin hole & replaces it with a cam pin socket and tapered cam pin design.

This new patent-pending design eliminates the natural weak point of Mil-Spec bolts by significantly increasing the amount of metal (& strength) at the cam pin location.

The result – No more broken bolts!

Additionally, the HMB Bolt reduces contact between cam pin & firing pin, enabling smoother operation of firing pin, bolt lugs & aft gas rings. The new cam pin socket also retains lubrication for extended operations.


  • 5.56 NATO – 223 Rem – 300 AAC
  • 9310 Steel
  • 4340 Hardened Steel Cam Pin
  • Nitride Black Finish

Additional information

Weight 14 oz

1 review for HM Defense HMB Bolt Carrier Group – Black Nitride

  1. 5 out of 5

    Robert P. (verified owner)

    Received correctly and love what I’ve read about the HMB BCG. Can’t wait to put it into action.

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