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What's the Difference Between 6061 and 7075 Aluminum

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If you are on the hunt for custom AR-15 parts, you've likely run into 6061 and 7075 aluminum references. And before getting too far into your search, it’s very important to know and understand the difference between the two.

For starters, most AR-15 parts are either 6061 or 7075 aluminum, popular for its malleability, strength and resistance to corrosion.  The question is normally what do the numbers mean and why does it matter.

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Crunching the Numbers

Aluminum is given numerical values based on the properties of the metal. The number refers to the amount of alloy agents present in the aluminum, which can make a huge difference in the strength and performance of the aluminum. The composition of each aluminum type includes the same list of alloys, but the amounts are quite different. Below are the alloys you will find in both 6061 and 7075 aluminum:

  • Magnesium
  • Silicon
  • Iron
  • Copper
  • Zinc
  • Titanium
  • Manganese
  • Chromium
  • Additional Metals

The Aerospace Specification Metals website offers additional information on the exact percentages of alloys in both the 6061 aluminum as well as the 7075 aluminum.

Getting to the Difference

The varying percentages of the alloys present in each type of aluminum give each different characteristics, but both are considered ideal for use in a variety of AR parts. 6061 aluminum is corrosion resistant and has great weldability with medium to high strength.  The 7075 aluminum offers similar qualities, but it adds a significant layer of additional strength and improved stress-corrosion resistance. Below are the mechanical properties for both the 6061 and the 7075:

6061 – Mechanical Properties

  • Ultimate Tensile Strength 45000 psi
  • Tensile Yield Strength 40000 psi
  • Fatigue Strength 14000 psi
  • Shear Strength 30000 psi
  • Hardness, Rockwell 40
  • Machinability 50%

7075 – Mechanical Properties 

  • Ultimate Tensile Strength 83000 psi
  • Tensile Yield Strength 73000 psi
  • Fatigue Strength 23000 psi
  • Shear Strength 48000 psi
  • Hardness, Rockwell 53.5
  • Machinability 70%

Making the Decision

Although some may argue for parts constructed with 7075 because of the added strength, the value of AR parts made with 6061 aluminum should not be discounted. Both aluminums offer quality and reliability, and ultimately it comes down to personal preference. When making your decision, consider what matters most to you. Ask yourself the following questions:

  • How will you use the AR
  • How much stress do you intend to place on the part
  • What budget would you prefer to stick to

Both aluminum options are extremely viable, and while the 6061 aluminum may seem subpar, that is certainly not the case. The added strength isn't a necessity, rather it is simply a bonus that some customers just prefer to have. There have been thousands of AR builders who have gone with the 6061 aluminum without any problems at all.

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Aside from only thinking about the qualities of the 6061 and the 7075, it is arguably more important to pay closer attention to the manufacturer. If you are purchasing your AR parts from a reliable seller, you are more likely to receive quality materials whether you choose the 6061 or the 7075. And when you shop with us, we stand behind every one of our products. The most important part of your decision is that you are comfortable and satisfied, and as a reliable retailer, we wouldn’t want anything less!

Our most popular and best-selling 7075 80% lower receivers are the AR-15 | Raw  80% Lowers. They are currently packaged together to save you money and so that you can knock out a few builds with a single order. 

They won't last long so get yours now!

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