The newly updated LM4 bolt catch is made of hardened metal and accepts a bolt catch spring, part 42, which is sold separately. The bolt catch fits all LM4 variants, including the LM4C and LM4 RIS, as well as the standard LM4 RIS.
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nThis part also appears as part 16 on the PTS MKM AR-15 and PTS MML Maten diagrams. Most internals for the PTS MKM AR-15s are compatible with LM4 parts.