Six Sigma Arms Lower Receiver

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At Six Sigma Arms we strive for perfection starting with the most critical component, the lower receiver. Regardless if you choose one of our custom guns, a fully assembled lower, or even a stripped lower, we want to ensure you enjoy years of accurate dependable service. There is extensive research put into every aspect of every component that goes into a Six Sigma Arms firearm, everything is done for a reason.

Six Sigma Lower

Six Sigma Arms lowers are forged from 7075-T6 aluminum which is the hardest aluminum alloy available. The dimensions are to the original blueprint to ensure compatibility with any aftermarket parts built within the original military specifications.

Six Sigma Lower

While maintaining compatibility with the original specification, several improvements have been made starting with the broaching technique used to shape the magazine well (be advised, our lowers are machined to EXACT specifications, "drop free" issues with some oversized polymer magazines have been reported). While more costly and time consuming it results in a stronger finished product by eliminating stress risers and the possibility of warping, distortion or cracking. The bottom of the magazine well has a deep bevel to enhance reloading. Additionally, the front has a checkered pattern for enhanced grip with the off hand.

Six Sigma Lower, front strap

We have also added a take up screw under the pistol grip to adjust the pre-travel of the trigger. This allows you to adjust the trigger feel to your liking. The walls of the trigger group area have also been strengthened.

Six Sigma Lower, trigger adjustment

To eliminate the possibility of lack of concentricity in the mating of the receiver extension tube and the lower, the buffer tube threads are reamed and bored based on the top of the receiver ensuring proper alignment of the buffer tube to within one - ten thousandth of an inch. The top of the receiver is used as the starting point from which all other dimensions are measured. This eliminates the possibility of tolerance stacking. This method is more expensive and time consuming than the traditional method several other manufacturers use.

Six Sigma Lower, buffer tube threads

Before we machine the lowers, they are cryogenically treated because it improves the dimensional stability of the lower resulting in a more accurate machining process. After machining, the lower is cryogenically treated once more to relieve internal metal stress and increase wear resistance.

Six Sigma Lower, selector markings

In the final finishing process, the lowers are stainless steel shot blasted and Level III hard anodized for an impressive durable rich black finish.

Six Sigma Lower, rollmark

The extra time, effort, and expense we go through during the manufacturing process ensures the highest quality, durability and reliability possible. Our customers appreciate and demand the very best and we work very hard to meet those stringent demands.

* Uppers with oversize lugs may need the lug lightly filed to fit.

Price: $250

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Please note: This order REQUIRES an FFL. Please have a copy of your dealer's FFL either faxed to 320.358.3080 or emailed (as a PDF) to sales@sixsigmaarms.com. We MUST have this documentation on file prior to shipping. Please contact us prior to purchase if you would like to pick up your order in person.

If you have questions we would be happy to answer them. Please contact us via our website or email us at sales@sixsigmaarms.com.