How to Machine an 80% Lower Receiver (AR15) Quick and Easy

Do you find it hard to machine an 80% lower receiver? You’ve undoubtedly figured out that building your new AR-15 or other rifle or pistol with an 80% lower receiver is definitely the ideal approach. You’ll escape the branded premium rates by avoiding the background check and NICS fees, as well as the transfer costs and additional taxes.  

In addition, we’re using the famous Elite Builder Jig, which includes an end mill and drill bits. This guide will show you how to use a drill press or a milling machine to finish your 80% lower. But how do you truly complete your 80% lower? At the end of this article, you will have enough knowledge and skills to machine an 80% Lower Receiver. Without further ado, let’s take a close look. 

How to Machine an 80% Lower Receiver (AR15) Quick and Easy

Tools Required

You need several tools to make the process easy and successful. Here are some of the must have items. 

• Drill press or milling machine.
• Vise. 
• Machining Oil.
• Digital calipers.
• Drill stop collars.

Step 1: Place the Lower on the Right Plate

Place the 80% lower on the right jig plate, with the pins within the rear take-down and away from the pivot pin holes. Mount the left jig plate on the opposite side of the assembly and stand it up upright.

Step 2: Mount the Plate Holder

After that, put the template plate holder in place. Place the holder on top of the jig such that the rounded edge of the holder rests against the buffer tube housing. Using the two largest hex-head bolts provided, secure the holder to the side plates.

Step 3: Carefully Install Hole and Vise

Install the plate into the holder with the two tiny countersunk hex-head bolts. “3/8 DR 2.00 DEEP FROM THIS FACE” is written on the first plate. After that, tighten the jig and place it in your vise to the machine.

Avoid over tightening the vise. To keep the jig from shifting while you work, only light pressure is required. The side plate will bend if the vise is over tightened. The jig and lower may get misaligned as a result of this.

Step 4: Mount the Drill Bit

Gather the 3/8 ” and install the drill bit provided into your drill press or milling machine. Drill through each pilot hole guide on the template plate into the 80 % lower receiver after aligning the jig and lower with your equipment. You must drill precisely 2.000 inches holes. From there, it would be better if you set the depth on the mill accordingly.

Step 5: Drill Holes to a depth of 2.000″

To extend the life of the bit, lubricate the plate and receiver using machining oil. This bit is required to complete the safety lever pin hole. Drill precisely 2.000 “from the face of the template plate, deep into the receiver. Set the depth stop on your drill or mill as needed, and check the final depth using a stop collar and calipers if necessary. Remove the 3/8” when all pilot holes have been drilled. Place the first milling template on top of the plate. 

Step 6: Mill Receiver to 1.375 Inches Deep

Use the short bit instead of the 3/8″ drill bit. Install the drill stop collar on the bit’s shaft and use your calipers to ensure the cutting depth is exactly 1.375″ from the template plate’s face. Allow the bit’s shaft to ride along the plate’s internal contour. This ensures that the receiver’s form is properly cut to size.

Apply a layer of machining oil or lubricant to the end mill bit, work area, and template plate. To avoid bit run-out and chatter, use this template to remove aluminum.

Step 7: Mill Receiver to 2.000 Inches Deep

The short bit and initial milling template can be removed now that the back shelf and a portion of the main cavity have been machined. Bolt the second milling template to the jig and install the extended 3/8″ end mill bit in the machine. 

Step 8: Cut the Trigger Shot

The 3/8″ end mill bit and second milling template can be removed once the main cavity has been cut to its full depth. Install the long 5/16″ end mill bit in your machine and the “5/16″ EM THRU BOTTOM.” This doesn’t require any precise measurements; simply cut a slot for the trigger in the receiver’s floor. The receiver’s firing control cavity will be complete once this final cut is done. To orient the assembly horizontally for drilling, remove the jig and lower it from the vise. Make sure the jig is facing the appropriate way. 

As you do it, you should avoid removing the template holder. The template holder serves as a vital link between the jig’s two side plates. By removing holder, the plate will be able to move independently of the other, which results in misaligned holes drilled in the components kit. Reposition the lower and jig in the vice horizontally, leaving the template holder fastened to the jig. Avoid over tightening the vise.

Step 9: Drill Hammer, Pin Holes

Only use the right side plate of the jig. Each pin hole will be aligned when it is completed thanks to the drill bushings. Make use of the 3/8 inches drill bit to complete the hole for the safety lever pin. 

Final Thoughts

Your 80% lower Receiver is now complete with the pin holes drilled! It’s now a fully stripped AR-15 lower receiver, ready for a parts kit installation. You can either paint the inside of the receiver or leave it bare to show off your craftsmanship. We hope that you enjoyed this informative article. After reading the step by step guide, you will have an easy time machining an 80% Lower Receiver in AR-15. You can comment if you have any suggestions regarding the above article. Don’t forget to like and share if this article was helpful.