---
title: CMMG MkG, MkGs, & Mk57 Platform Specifications
description: "Bolt Carrier Group Materials: Bolt – Steel, 9310 Carrier – Steel, 8620 Extractor – Steel, S-7 Ejector – Steel, S-7 Currently available in the following calibers: 45ACP(MkG) 9x19mm (MkGs) 5.7x28mm (Mk5"
---

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# CMMG MkG, MkGs, & Mk57 Platform Specifications

Bolt Carrier Group Materials:

Bolt – Steel, 9310

Carrier – Steel, 8620

Extractor – Steel, S-7

Ejector – Steel, S-7

Currently available in the following calibers:

45ACP(MkG)

9x19mm (MkGs)

5.7x28mm (Mk57)

Virtual Patent Information can be found [here](https://cmmg.com/patents).

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