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How to Complete an 80% 1911 Frame

How to Complete an 80% 1911 Frame

Posted by 80 Lower Jig, Co. on Sep 8th 2020

You want to own America's favorite handgun - congratulations! It's a smart decision. But do you want to buy some random piece off the gun store shelf? Risk having a mediocre .45 (or 9mm)? Nobody wants that, the 1911 is legendary. Today, we're showing you how to instead build John Moses Browning's greatest creation from scratch, using an 80% 1911 frame.

Building a 1911: The legal stuff

First thing's first: A lot of people ask, "can I build a gun at home?" The Bureau of Alcohol, Tobacco, and Firearms (ATF) has this say to on the subject:

“No, a license is not required to make a firearm solely for personal use. However, a license is required to manufacture firearms for sale or distribution. The law prohibits a person from assembling a non–sporting semiautomatic rifle or shotgun from 10 or more imported parts, as well as firearms that cannot be detected by metal detectors or x–ray machines. In addition, the making of an NFA firearm requires a tax payment and advance approval by ATF.”

[18 U.S.C. 922(o), (p) and (r); 26 U.S.C. 5822; 27 CFR 478.39, 479.62 and 479.105]

The 1911 is not:

  • A shotgun
  • An NFA gun
  • A non-sporting semiautomatic rifle
  • A gun built with 10 or more imported parts
  • A gun that can’t be detected by metal detectors or X-rays

We’re not building our 1911 to sell it, and we have no intentions of doing so. So, we’re in the clear as far as Federal law is concerned.

State laws

Some states have special restrictions against building guns at home, especially handguns. California, for example, only allows specific handgun makes and models that have been tested for certain safety requirements to be legally owned in the state. Unfortunately, that excludes the 1911 frame blank. Check your local and state laws before building. Moving on, let's look what what parts we need:

Pistol Assembly: Parts Needed

Here’s what you’ll need to build your gun from scratch. The first two components of the project, the frame blank and parts kit, are caliber- and frame-specific and must correspond with each other. For example, if you want to build a classic, G.I.-style gun chambered in .45 APC, you’ll need a 5” Government frame blank and 5” Government Parts Kit. The same rules apply for Commander and Officer models, as well as variants chambered in 9mm or .38.

"Are these 80% 1911s compatible with retail parts?"

Yes. If you wanted, you could just buy a frame and jig, complete the frame, and then buy all the parts you'd need from wherever else. But the parts kits, barrels, and slides included with the frame blanks are specifically machined to ensure tolerances are perfect for final assembly. If this is your first time owning or building a 1911, we recommend purchasing the parts included with the full build kit.

Frame blank vs. Retail frame

Speaking of aluminum, the 1911's 80% frame is not made out of steel. Instead, these blanks are made from forged, mil-spec aluminum. This is no different than using a typical 80% lower used to build an AR-15. This aluminum construction provides some big advantages, the biggest being weight savings. The aluminum frame weighs around 60% less than a store-bought, steel frame. That's a huge reduction in weight, making the finished gun more comfortable and ergonomic without sacrificing reliability.

And since the frame blank isn’t a firearm, it can be bought, sold, and shipped to you without having to deal with the ATF or an FFL. Nothing else you’ll buy for this project is considered a firearm either, including the parts kit and jig.

Cutting and Drilling the Frame

Now that we’ve cleared up the legal stuff and figured what you what you need for the build, let’s get started! These instructions are to be used only with the Phantom 1911 Jig by Stealth Arms. Other 1911 jigs may work differently:

1: Insert 1911 frame into Phantom Jig

The Phantom Jig secures your frame blank using two provided dowel pins and one Allen-head set screw. Seat the dowel pins into one of the two plates as pictured. Let your frame slide onto the dowel pins and then sandwich the frame using the other plate and set screw.

2: Drill the hammer and sear pin holes

Insert the aluminum spacer into the slot in the left jig plate. Tighten the jig and frame in your vise via the left plate. Ensure the assembly is perfectly level. Use the larger drill bit (#22) to drill half-way through the frame via the appropriately sized guide hole in the right plate. This is the hammer pin hole. Drill half the sear pin hole using the smaller drill bit (#35) and smaller guide hole. Flip the frame and jig over and relocate the aluminum spacer into the slot on the right plate. Re-tighten the assembly in the vise using the right plate, and finish drilling both holes into the frame using the guide holes on the left plate.

WARNING: Don’t attempt to drill all the way through the frame on one side. Your drill bits will flex and create poorly drilled holes, which could ruin your frame.

3: Set up the cutting car

This is the manual cutter used to finish the slide rails and barrel seat. The car already has the slide rail and barrel seat cutting blades installed, but they need to set before you begin cutting. Loosen the Allen-head set screw securing the slide rail cutter and carefully push the blade up into the car so the blade’s edge is slightly protruding from the bottom of the opening. Re-tighten the screw. Next, thread the cutting handle and adjustment knob atop the car. You’re now ready to find your starting point for cutting.

4: Set up the jig for cutting

Place the aluminum spacer in the left jig plate. Secure your frame and jig in the vise using the left plate, with the barrel end toward you. Apply some of the oil in the small plastic bottle to the slot on the right plate, and the entire surface of the plate. This surface contacts the cutting car and needs ample lubrication to allow the cutter to glide freely.

5: Set the initial cutting depth

Rest the cutting car atop the jig, with the blade resting inside the slot. Gently push the cutting car forward while turning the adjustment knob clockwise. This will begin bringing the cutting blade in contact with the frame. Continue rotating the knob until the blade contacts the frame. You will feel resistance while pushing the cutter once the blade touches the frame. Stop moving. This is your initial cutting depth. Once you’ve found the starting position, grab a marker. Place a mark on the jig wherever the white dot on the adjustment knob is resting.

Measuring slide rail cutting depth

The notches surrounding the adjustment knob represent 1/10 of a full rotation of the knob. The knob must be rotated 19 times (1.9 revolutions) to achieve the slide rails' depth of 0.61”.

6: Cut the slide rails

Once you’ve found and marked the starting position of the knob, start cutting the slide rail by pushing the car forward across the frame. Make 3 to 4 passes before rotating the adjustment knob clockwise one notch. Lift the cutter slightly when bringing it back toward you; dragging it backward will ruin the blade. Be sure to clean out metal shavings as you cut. It’s important to reapply machining lubricant while you cut. You must make one full rotation of the adjustment knob followed by 0.9 additional rotations, stopping at the notch before your marked starting position.

Once one side of the frame is cut, loosen the jig and reposition for the opposite side. Repeat steps 4 and 5 for the opposite side of the frame.

7: Set up the jig for barrel seat cut

Once both slide rails have been cut to 0.061”, disassemble the frame and jig and re-position the dowels pins in the side plate as shown. Re-secure the frame and jig atop the guide pins, and re-seat the jig with the provided set screw.

8: Secure the jig and vise for barrel seat

Secure the frame and jig vertically in a tabletop vise, like shown. The barrel end of the frame should face toward you.

9: Set up the cutting car for barrel seat

Remove the adjustment knob and handle from the cutting car. Re-position both on the left side of the car. Repeat step 5 to find the initial barrel seat cutting depth. We need to set up the other blade for the barrel seat like we did with the slide rail blade. Loosen the set screw for the blade and position it so the blade is just barely protruding from its mount, then re-tighten the set screw. With the adjustment knob, handle, and blade tightened, rest the car on the frame like shown in step 8, and begin slowly pushing the car forward while rotating the adjustment knob clockwise until you find the blade's starting position. Again mark the cutter wherever the white dot on the knob aligns with the adjustment notches.

10: Cut the barrel seat

Repeat step 7 and cut the barrel seat to a depth of 0.077”. This is achieved by making 2.4 complete rotations of the adjustment knob, or 24 notches. Mark the starting position and make 3 to 4 passes, lifting and lubricating as needed until cutting is complete.

Tips for Cutting

Some users have reported difficulty achieving the right cutting depth when completing the barrel seat. Others have reported issues with the blade. To ensure your barrel seat is properly cut, double-check and re-tighten the blade as needed. It may come loose during cutting. The blade has two right-angle shoulders that are meant to be stops. If your cutting the seat and approach these shoulders on either side of the blade, stop cutting. You've reached the final depth.

Your 1911 frame is complete!

Once you’ve finished cutting the barrel seat, you’ll be the proud owner of a real, functional 1911 frame. At this point, you’re now the owner of a firearm in the eyes of the ATF. And now, you must observe all applicable gun laws. But now comes the fun part: Finishing your 1911 and hitting the range. All you need to do now is install your 1911's parts kit, which includes the barrel and slide.

Install your 1911 Parts Kit

Like we said, your completed 80% 1911 frame functions exactly like a retail or store-bought 1911. The parts kit installation is just like any other 1911 you've put your hands on. If you're not familiar with the installation procedures, there are plenty of resources online (trying to provide every step and photograph in this guide would be unfeasible). One of our customers, Sterling Archer, created a wonderfully paced, easy-to-follow instructional video. Check it out here if you need detailed instructions to complete your installation.


Equipped with our guide, you should be able to master your 1911 build and create the perfect G.I. or compact shooter. If you have any questions about purchasing or finishing a frame blank, using the Stealth Arms jig, or assembling your parts kit, just give us a call or email us. We build our own guns, too! We're glad to help.

DISCLAIMER: If you are new to the world of DIY gun building, you likely have a lot of questions and rightfully so. It’s an area that has a lot of questions that, without the correct answers, could have some serious implications. At, we are by no means providing this content on our website to serve as legal advice or legal counsel. We encourage each and every builder to perform their own research around their respective State laws as well as educating themselves on the Federal laws. When performing your own research, please be sure that you are getting your information from a reliable source.

We are a national retailer of individual components and not all products depicted on this website are legal in every state. Shipping of various products found on this website are prohibited to some states (such as California, Connecticut, District of Columbia, Hawaii, New Jersey, New York, Rhode Island, and Washington). The information, pictures, text or products presented on this website are not a representation by us, and should not be understood by you, that any product or completed firearm is legal to assemble or own in your state of residence. We encourage each and every builder to perform their own research about the state and federal laws that apply to them. It is your responsibility to understand the law and we encourage you to consult with an attorney or your local ATF representative.