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CMMG, Inc MK3 Lower Parts Kit Up to 35% Off w/ Free Shipping — 2 models

CMMG, Inc Gunbuilder's Lower Parts Kit, MK3, 38CA61A
CMMG, Inc .308 Lower Parts Kit, MK3, 38CA6DC
CMMG, Inc Gunbuilder's Lower Parts Kit, MK3, 38CA61A
1 of 2 images
CMMG, Inc Gunbuilder's Lower Parts Kit, MK3, 38CA61A
CMMG, Inc .308 Lower Parts Kit, MK3, 38CA6DC
2 of 2 images
CMMG, Inc .308 Lower Parts Kit, MK3, 38CA6DC

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Questions & Answers
Will this work on a sig tread 716? Expert Answer

The CMMG, Inc MK3 Lower Parts Kit should work fine on a Sig Tread 716.

by Hunter, Gear Expert, August 22, 2022
Hi can you please help, this is my first AR-10 M5 308 that I going to build and I concern if this lower kit will fit on it Expert Answer

Please email us at techsales@opticsplanet.com so we can further answer your question.

by Ben, Gear Expert, February 16, 2021
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Customer Reviews
Helpful Positive Review
Fits great by whatitisholmes, November 4, 2023
Used to complete an 80% DPMS, everything fit great. The bolt catch pin is threaded so make sure your lower is set up for that before you buy and you’ll be in good shape. I oiled every pin and spring as I put them in, it is an absolute must do. Cycle ...
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1/1 found this helpful
Helpful Positive Review
Fit perfectly in a Aero Precision M5 lower by Watt, Verified Owner, May 18, 2022
fit and finish are great, had a threaded pin for the bolt catch. The included trigger and grip feels great and everything was package in its own color coded bag. Expected to have issues with fitment since it's a .308 platform but it all fit great.
3/3 found this helpful
Helpful Positive Review
CMMG .308 Gun Builder's Lower Parts Kit 38CA61A by Crocket, Verified Owner, April 8, 2022
I used this kit for a recent LR308 build - everything fit perfectly. However, the most impressive thing about this parts kit is that CMMG had the foresight to package the parts in a plastic form that holds the parts over a card with each part labell...
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1/1 found this helpful
Helpful Positive Review
Fit perfectly by Jon, Verified Owner, February 20, 2022
Exactly what I needed to finish my 80% lower. Had no issues what so ever mine came with and extra spring for the bolt catch pin. The cmmg video for installation is a bit lacking. Seems to function properly haven't shot the rifle yet waiting on a buff...
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1/1 found this helpful
Helpful Positive Review
Wrong rear takedown pin in kit by Brad, November 7, 2016
Received the kit as promised. Unfortunately the rear takedown pin was wrong. The one in the kit was .250" for an AR15. Rather than hassle with returning to Optics Planet, I called CMMG directly. Thumbs up to them for their customer service. They ap...
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10/10 found this helpful
Helpful Positive Review
Perfect kit for your 80% lower by Kyle, November 4, 2020
I ordered this kit for a build I’ve been working on. Quality of the parts seem good and everything was included to finish. Fit perfect in my 80% arms lower receiver. I highly recommend this product if you’re in the market to complete your 308 build!
1/1 found this helpful
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Product Info for CMMG, Inc MK3 Lower Parts Kit

Contains the necessary parts to complete an LR308lower receiver besides the receiver extension and butt stock. Building on the mil-spec standard, CMMG Gunbuilder's Kits include everything you need in a new or custom lower build where you add the trigger, pistol grip and trigger guard of your choosing. Basic parts list: takedown pin, safety selector, bolt catch, receiver pivot pin, selector detent, bolt catch plunger, takedown pin detent (2), magazine catch, bolt catch spring, takedown pin detent spring (2), magazine catch spring, bolt catch screw, hammer and trigger pin (2), magazine release button, buffer retainer and buffer retainer spring.image

Specifications for CMMG, Inc MK3 Lower Parts Kit:

Manufacturer: CMMG
Color: Black
Finish: Black
Gun Model: CMMG Mk3
Condition: New

Package Contents:

  • CMMG, Inc MK3 Lower Parts Kit

CMMG, Inc MK3 Lower Parts Kit Orderable Models

List of Orderable Models

  • CMMG, Inc Lower Parts Kit, MK3, Gunbuilder's kit, 38CA61A , MPN: 38CA61A , UPC: 815835015415 , Code: 2CM-LPK-3MNB-38CA61A
  • CMMG, Inc Lower Parts Kit, MK3, 38CA6DC , MPN: 38CA6DC , UPC: 852005002097 , Code: 2CM-LPK-3MNB-38CA6DC

CMMG, Inc MK3 Lower Parts Kit Unavailable & Discontinued Models

List of Unorderable Models

  • USED, CMMG, Inc Lower Parts Kit, MK3, Gunbuilder's kit, 38CA61A , MPN: 38CA61A-EDEMO , Code: 2CM-LPK-3MNB-38CA61A-EDEMO-RE-B
  • CMMG, Inc Lower Parts Kit, MK3 w/Ambi Selector, 38CA65F , MPN: 38CA65F , UPC: 815835014777 , Code: 2CM-LPK-3MNB-38CA65F
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Last updated 2026-07-20 UTC.