CMMG .308 Lower Receiver Parts Kit


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All the Parts You Need to Get Started on Your Next Mk3 Build

Combine this kit with a buttstock kit to complete your lower group. Compatible with CMMG Mk3 Lowers and most LR308 type lowers.

All parts meet or excede mil-spec.

The CMMG Lower Parts Kit for the MK3 contains 4 color-coded bags:

  • The Clear bag contains the .308 takedown pin. .308 receiver pivot pin, two (2) takedown pin detent, two (2) takedown pin detent springs.
  • The Yellow bag contains the bolt catch, bolt catch plunger, both catch screwm bolt catch spring, buffer retainer, and buffer retainer spring.
  • The Red bag contains two (2) hammer and trigger pins, hammer spring, trigger spring, disconnect, and disconnect spring.
  • The Blue bag contains the magazine catch, magazine catch spring, and magazine release button.
  • The Green bag contains the safety selector, selector detent, selector detent spring, lock washer, and pistol grip screw.
  • Hammer, trigger and pistol grip also included

Have Questions About this Product?

The AT3 Tactical store has a 90 day no-hassle return policy for products in good condition. You can view the full details of our return policy here.

If you encounter an issue or defect with a product after 90 days of your purchase, you can refer to the manufacturer for a warranty claim. Their policies are below.

CMMG Warranty

Seller warrants to Buyer that for a period of 6 months from the Delivery Date, all Goods will be:

  • Free from any defects in workmanship, material, and design
  • Conform to applicable specifications[, drawings, designs, samples and other requirements specified by Buyer]
  • Fit for their intended purpose and operate as intended
  • Merchantable
  • Free and clear of all liens, security interests or other encumbrances
  • Not infringe or misappropriate any third party’s patent or other intellectual property rights.

Inspection and Rejection of Nonconforming Goods

The Buyer has the right to inspect the Goods for a period of thirty (30) days after the Delivery Date. Buyer, at its sole option, may inspect all or a sample of the Goods and may reject all or any portion of the Goods if it determines the Goods are non-conforming or defective.

If Buyer rejects any portion of the Goods, Buyer has the right, effective upon written notice to Seller, to:

  • Rescind the Order in its entirety
  • Accept the Goods at a reasonably reduced price
  • Reject the Goods and require replacement of the rejected Goods.


If Buyer requires replacement of the Goods, Seller shall, at its expense, promptly/within 30 days replace the nonconforming Goods and pay for all related expenses, including, but not limited to, transportation charges for the return of the defective goods and the delivery of replacement Goods.

If Seller fails to timely deliver replacement Goods, Buyer may replace them with goods from a third party and charge Seller the cost thereof and terminate this Order for cause pursuant to Section 20.

Any inspection or other action by Buyer under this Section shall not reduce or otherwise affect Seller’s obligations under the Order, and Buyer shall have the right to conduct further inspections after Seller has carried out its remedial actions.

Disclaimer: Manufacturer’s warranty is subject to change without prior notice.

Customer Reviews

Based on 1 review
Doesn't fit. Be wary.

Not sure what went wrong, all the detents in this kit were slightly smaller than they were supposed to be. I pulled apart another 308 lower i had, to compare the parts to the ones that came with this, all the detents were just enough off in size to not function correctly. Ended up using another brand parts kit to finish the rifle.

Sorry to hear about the issue, Lee. I sent you an email to resolve the issue.