How To Finish An 80 Lower
Dec 17, 2013
Finishing a lower requires a milling auto or drill printing, a fixture if you choose the drill press method, some drills and end mills and very basic machine skills. You lot're non going to save money. The beautiful barracks lowers in the pictures came from Juggernaut Tactical. They currently sell the fourscore percent lowers for $155 and CNC-finished lowers for $165, so price isn't a gene.
I think well-nigh people tackle a projection like this because they like making their ain stuff. It's the sense of achievement more than anything else. It's going one step further than simply assembling a burglarize kit from finished parts.
Over the years, I have built several 1911 pistols for my personal use. I didn't relieve whatsoever coin. In fact, a gun assembled from individually purchased parts may cost yous more than a manufactory-built firearm. Still, there is that satisfaction of building your own.
Finishing 1 of these receivers on my Grizzly Mill/Drill was not a big chore. AR-15 lower receiver blueprints are readily available online, and my main concern was calculating the dimensions from the drawings correctly. The holes for the selector (3/8") and trigger and hammer pins (5/32") were drilled first and they must exist precisely positioned for proper function of the fire control group.
Once the holes were done, it was only a thing of milling out the receiver pocket with a long 7/16" end factory and finally cut the slot for the trigger with a long 5/sixteen" end manufactory. Within dimensions of the pocket are not super disquisitional, and a few thousandths error probably won't exist noticed.
One mistake I made was not cutting the rear channel deep plenty into the buffer tube threads, and when I checked the fit of an upper receiver the takedown pivot wouldn't quite line upwards. I milled in a little more clearance and the problem was solved. I would rate finishing one of these receivers on a mill equally well within the capabilities of whatever hobbyist with basic machine skills.
Finishing a lower on a drill press is besides possible. You will need a fixture that consists of plates that clench around the receiver to guide the drills and end mills. The fixture from Juggernaut Tactical is very well fabricated with the side plates drilled for right positioning of the trigger pin, hammer pin and selector holes.
Three separate elevation plates are included for dissimilar steps of the machining process and a tool kit is available with the fixture which includes the drills and terminate mills yous volition need. Almost of the aluminum is removed by drilling overlapping holes with progressively larger drills.
It is important to exist able to set the depth on your drill press accurately with a dial caliper. In the concluding steps, the drill printing is used as a router as the fixtured receiver is clamped in a vise and moved around the cutter following the pattern of the top plate.
You will need to maintain a solid grip on the vise as yous movement it around on the drill press table using the slots in the fixture equally a template. A good video of this operation is available at the Juggernaut Tactical web site.
Test-fit an upper receiver to the lower when you call back it is finished to make sure the takedown pin holes line upwardly and the upper slides into position easily. Also, test fit a standard mil-spec hammer, trigger and selector to cheque part of the fire command group. The freshly drilled trigger and hammer pin holes will non be anodized against wear, and so non-rotating pins may be a practiced thought for the final build.
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Here'southward the raw lxxx% receiver equally received from Juggernaut Tactical. The offset pace in the process is drilling the hammer pin, trigger pin and selector holes.
Norcross says finishing an 80% receiver is non a challenging job, only care must be taken to properly position the drilled holes. Check your measurements.
The receiver pocket is milled out with a long seven/16" end mill. Watch your depth! Keep in mind that the freshly cut parts surfaces will accept no anodizing.
The finished receiver pocket. Groovy. With a secure setup and proper tool speeds, you can cut a nice, shine pocket that looks equally adept as the factory version.
A hammer, trigger and selector are examination-fitted to the completed receiver. Everything fits. A properly fitted 80% receiver can look every bit good as the factory unit of measurement.
If yous finish your receiver in a drill press a fixture will exist required. Annotation the conspicuously marked holes on the Juggernaut fixture. You can't screw it up.
Source: https://www.firearmsnews.com/editorial/finish-80-ar-15-lowers/78212
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