80% Lower Guide
What is an 80 Lower?
The receiver or frame is the part of the firearm that can be controlled by the Gun Control Act of 1968, the same act that ensures your right to manufacture firearms at home. An 80% lower is a receiver blank that is machined as far as you can without legally becoming a frame or receiver and would then require to be transferred to an FFL. A lower parts kit will not even fit in an 80% Lower until it has been machined into a complete firearm.
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Manufacturing 80% Lowers Since 2009
The 80% AR-15 Lower Receiver started it all, this was the first commercially available receiver on the market and had a determination from the ATF saying it was not a firearm. We lead the way by including a flared magwell, using high quality aluminum products and cnc machined the lower receiver on our milling machine. Every receiver we manufacture meets our precise quality control standards.
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Quality from Start to Finish
Currently all 80% AR 15 receiver options from Tactical Machining are CNC machined from 7075-T651 Aluminum Cerro forgings. For our 308 Lowers we have two options, a billet aluminum 7075 option and a Cerro 7075 forging like our AR-15 platform. The 10/22 platform is made from 6061 aluminum made in the USA. The TM Recon and TM Government 1911 frames are made from investment castings. Unlike some of our competitors, our investment castings are made in the USA and then CNC Machined in-house in the USA. Many 1911s are made from Korean castings and then machined in the USA by the Korean company’s USA division.
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Billet lowers vs Forged lowers
What is a billet or what are billet lowers? A billet is a term for a solid block of metal with no features at all, almost as raw as metal can get. A forging on the other hand is a piece of billet that has been pounded into shape by a die on a forging press. It requires less machining because it has been shaped into a receiver blank, and has the advantage of the metal grains following the shape of the part. But that really doesn't mean all that much except to your wallet. Forgings offer significant cost savings and no real drawback.
Our AR-10 lowers are both offered as forged lowers and billet lowers depending on what your price range is. Cosmetics aside, there isn't a huge difference between billet aluminum and forged aluminum other than price and freedom of design. With that said, the billet lower receiver does have the advantage of having all sides machined in the milling machine and in some cases allows you to add features like an extremely flared magwell or an ambidextrous bolt catch. A billet lower receiver normally is purchased because of it's cosmetic appeal. Other manufacturers offer a billet lower receiver that may suit your needs, we only offer billet aluminum options in the TM-22 and AR-10 platforms. Some forgings are designed for companies and include those features like the flared magwell as well. Again, it really is a draw, there is no clear winner here.
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Coating Options
Many of our platforms include the option for an anodized receiver or a raw aluminum receiver. After our parts have been cnc machined they are then taken to laser engraving if necessary and finally sent off to be coated. There are several real coating options both commercially available and available for the home gunsmith.
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Raw Aluminum Finish
Simple enough, some people don’t coat their 80 lowers and may elect to leave the raw aluminum finish or even polish it.
Hard Coat Anodizing
Mil spec Hard Coat Anodizing is a great option and will match any of the ARs already in your collection and many of the parts purchased from other companies. It is an extremely durable coating and has extreme hardness and great wear resistance. It isn’t easy to hardcoat anodize at home and is best purchased that way or by bringing your completed firearm to a local anodizer.
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Type 2 Anodizing
Type 2 Anodizing can be performed at home, color options are close to unlimited but isn’t as wear resistant or as tough as hard coat. I would consider it middle of the pack for a coating option. Better than bare aluminum not quite as good as hard coat or Cerakote.
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Cerakote
Cerakote is the trendy coating right now and can be applied at home or before your lower is machined. If I were to pick a coating for the home gunsmith this would be the first choice. It is the priciest to complete and the priciest to get the tools to complete but the color options are unlimited, and the performance is close to anodizing.
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Spray Paint
Spray paint from your local hardware store works pretty well believe it or not. Make sure you prep the lower and remove all oils and grease. After that I like to bake the lower to about 150-200 degrees and then paint it. It will not adhere great and will rub off easily like type 2 anodizing but it is cheap and you can always repaint it.
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Custom Laser Engraving
Custom Laser Engraving 80% Lowers is all the rage nowadays. We were the first manufacturer to offer custom engraved 80 lowers and have since expanded our laser engraving operations. We have continuously expanded the option to add laser engraving to our products. If you’re interested in custom laser engraving 80% lowers we have a number of selector markings to choose from and in some cases can add pre done artwork to your lower. More elaborate artwork can be done as well but it is a case by case basis.
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Completing an 80% Lower Overview
An 80 lower leaves just enough to allow the home builder to use a drill press, router jig, or jig kit to complete at home. There are many jig options for each platform, which we will cover below. We’re going to cover many of the considerations you should consider when doing these projects. With that said, we will cover the tooling you need as well.
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80% receiver Jig Options
There are a few basic ways that the home enthusiast can complete an 80 lower receiver. Right now, the most popular way is to use a router jig and a drill press. For AR lowers the main methods are below.
Completing an 80% Lower without a receiver jig
The most difficult is no Jig, many people complete the lowers this way, but it is truly difficult to do unless you are a skilled machinist. Essentially you would use your mill and rudimentary fixturing like C Clamps, vises and 3-2-1 blocks to orient your part and mill the features. In order to ensure your drill bits hit the right spot, you'd have to count the turns on your bridgeport handles or rely on your digital read out.
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Consumable Tooling
Consumable tools are what is used in the machines to complete the lower or receiver. Some examples of consumable tooling are Drills, End Mills, Keyway Cutters, Ball End Mills, Counter Sinks, etc. Each platform requires different tools to complete. When selecting drill bits and end mills for your kit, be sure that they will work for milling and drilling the product you have. If you're milling with an end mill too short, you will not be able to reach the required depth, the same goes for drill bits, they must reach.
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Consumable Tooling for AR Lowers
Consumable tooling is fairly well thought out for the AR platform and is pretty universal. Most you can use any drill you choose that meets the length of cut requirements. Some jigs, like the 5D Tactical jig have extremely specialized end mills used in their system and require you to use their end mill. Other jigs use very generic tooling, I recommend sticking with what the manufacturer of the jig kit recommends or finding a very similar replacement. On an AR you will need the following tooling:
- 5/32 Drill bit or Similar for the hammer and trigger hole
- 1/4 Drill bit or similar for removing the material from the trigger pocket before milling
- 3/8 Drill bit or similar for the safety selector
- End mills appropriate to your jig kit for milling the fire control group. We recommend a 5/16” end mill for our jigs.
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Consumable Tooling for a 1911 Frame
The tooling for a 1911 frame isn’t anywhere near as standardized as the AR lower, what we recommend is below. It also typically isn’t as affordable as the AR lower tooling. This is because it is a more difficult product and can require more specialized tooling. It is highly recommended that you use a milling machine for the 1911 frame project.
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You’ll need the following tools at minimum:
- 3/32 width, 3/8 Diameter key seat cutter
- 18mm Ball end mill
- 4mm or .1575 drill
- .110 or #35 drill
With that said, Stealth Arms produces a set of tooling for manufacturing a 1911 frame without using a mill. We haven’t used it here at Tactical Machining but have had some customers say it is doable and takes a while. If you don’t have milling experience, it very well may be a good option.
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Milling Anodized vs Raw Aluminum 80% Lowers
The market has been trending towards purchasing 80 lowers that have already been anodized black. One of the challenges of the past was finding a way to coat your 80 lower once you were finished milling the 80 lower. Some would spray paint their lowers, leave them unfinished and others would bring their lowers to an anodizer and wait on premises for them to be anodized black.
Now, you can purchase a lower that has been anodized black and then complete the milling on it. Be warned, if you order an anodized 80 lower it will ruin the anodized finish where the milling is performed, and you may want to coat it with something to prevent corrosion.
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Parts and Accessories
The good news is the AR-15 upper receiver and all the other parts are completely uncontrolled as if it was a receiver blank. Even complete uppers are not controlled. This is great news for the home gunsmith as it opens up your options on what you can purchase. Many companies offer complete uppers which are ready to bolt on to your lower, or partially complete uppers that are in need of just a bolt carrier and a charging handle. We manufacture our own stripped upper receiver from both billet aluminum for our 308 ar lowers and an aluminum receiver blank or forging for our AR-15 line. We plan on adding complete uppers in 2020 and just recently started offering AR-15 handguards in late 2019.
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80% Build Kits
Our 80% build kits include an upper receiver that we manufacture and also include our handguard. You can acquire your own parts or parts kit and then add it to the build kits to create your own rifle. If you want to simplify your purchase, check out our 80% Build kits. This isn't to be confused with a rifle kit which includes every part to build an AR Platform firearm. This is just the core components, an upper, lower and handguard.
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