Watercooler 5/17 Open Thread: The Lunch-Hour Lower


Lunch Hour Lowers: Flipping Schumer and Bloomberg Off With a “Ghost Gun” On One Hour A Day

This month we’re going to do something a little different for Guns & Gear Reviews, a little project I started last week called “Lunch Hour Lower”–completing an AR15 lower receiver from a ship-to-your-door 80%-ready “blank” on one hour a day using only one toolbag of readily-available tools (hence “Lunch Hour Lower”). There won’t be any assembly instructions here (Brownells has far better ones than I could ever write and I’ll link them in Part 2 next week), this is just me inviting you to look over my shoulder as I attempt to complete a polymer lower using only an inexpensive jig, a cordless drill and my pocketknife. I should note that this lower had a little head start, I had bored the entire selector hole and about 1/3 of the way down for each end of the trigger slot by hand, and also a handicap since I preferred to punch the selector, triger-pin, hammer-pin and trigger-slot holes all the way through the solid block rather than drill them after milling out the Fire Control pocket. Also, I should note that since plastic is weaker than Mil-Spec 7075-T6 aluminum and since I didn’t have a ruler that could do thousandths of an inch, I rounded the pocket depth off to a slightly-shallower-than-normal 31 millimeters rather than the specified 1.249 inches.


For the record, it is completely legal to manufacture a firearm for personal use, as long as you comply with Federal and local laws and do not intend to “engage in the business”–ATF has a thorough Question & Answer section here.

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Before and After. Top/left to bottom/right: raw blank as received (other than filling in inappropriate “Auto” seleector marking), blank in jig ready to start work, finished lower. Author photos.

  • Day One: FCG-pin holes: Punched all the way across the unmilled blank, smooth as if the drill was riding on oiled glass rails. Trigger slot ends: Took some doing, but doing a pilot bore with my 3/32 bit, then the 1/4 then the 5/16 got ’em. Useful lesson learned: ‘Reverse’ has more use than just screws, it can also be used to extract debris, or the bit, from the bore. Trigger slot, space between ends: OOPS. Little web between the holes is putting up a BIG fight, only have it knocked down to about 1/3 of the way through. Lesson learned: drill pilot hole at slot center in addition to ends, and start boring it first.All in all, a fairly productive lunch-hour… even though power tools seem a lot harder work than the last time I used one in Shop class 20 years ago.
  • Day Two: Trigger-slot web between end holes taking forever to go down. Next time, center FIRST then ends. Ditto “tail” of FCG pocket–next time “unguided” front-half first, then finish with jig-guided rearmost section. End mill bit plus cordless drill = No Bueno. Must remember to pick up drill stand and small vise. Drill is getting heavy and tiring. But I wouldn’t be doing this if it were EASY…
  • Day Three: So, using my fancy-a** end-mill bit won’t work without further tool purchases. Workaround: Do it just like the early 80-percenters did, with lots of little holes. Have starters for a ring of 3/32’s all the way around the FCG pocket and pilots for 1/4’s at the corners, and at the same time I’m going to work out from the bored-through trigger-slot hole using my 5/16 and 3/8 bits. If all the end-mill has to do is smooth out the bottom, that shouldn’t be too much work, right? Onward. Improvise, Adapt, Overcome!
  • Day Four: End-mill still required, just needs some warm-up acts before the Main Event. Missed spacings on a few of the Swiss-cheese holes, so having to SLOWLY grind those down until I can chisel and pry-bar them down. Other than two annoyingly determined cross-bars of plastic, one behind the trigger slot and the other at the front of the trigger/safety “tail,” down to about 1/3 of the FCG pocket to go. FCG sorted into four distinct “sections” each taken down about halfway to goal: trigger-tail (full depth) behind trigger slot, trigger slot and before TS. Each are separated by thick webs of plastic where I should have drilled more pilot holes. Still making headway, still learning–“this works, that coulda been thought out/done better.”
  • Day Five: Entire FCG pocket milled to 25mm depth aside from a few problem areas. “Webs” between pocket sections gone. Front section ready for hammer install… trigger area needs to come down four more mm minimum. (I’m working to “minimum parts clearance plus a hair of movement room” rather than AR TDP… I DO NOT trust this lower, especially with some early mistakes I made machining it, and am hoping that extra material will add some structural strength to help compensate.)
  • Day Six: NOTHING accomplished. No machining operations due to the Evil Old Crab deciding to telecommute from home and insisting on absolute silence, never mind me having MY OWN business to do. “Why can’t you go to your own office like a civilized person?”
  • Day Seven: Bottomed out and “tail” floor lowered to depth of main pocket. Ready for assembly and function testing upon arrival of KNS Precision non-rotating fire-control pins.

Next week we’ll  discuss the lessons I learned from this exercise, but for right now we can close this week by noting that the last time I touched power tools was in Shop class sometime in the mid-1990s, so if stub-fingered, shaky-handed me can do it, you can too.



This Week In History

  • Sunday, 5/14: Constitutional Convention convenes, 1787; Lewis & Clark Expedition sets off, 1804; Skylab launched, 1973
  • Monday, 5/15: Virginia instructs representatives to propose independence resolution, 1776; USDA forerunner Bureau of Agriculture authorized, 1862; Standard Oil ordered broken up, 1911
  • Tuesday, 5/16: First Oregon Trail wagon train departs, 1843; Navy NC-4 seaplane starts first trans-Atlantic air crossing, 1919; first scheduled direct NYC-London commercial flight, 1951
  • Wednesday, 5/17: New York Stock Exchange formed, 1792; first Kentucky Derby, 1875; Watergate hearings begin, 1973
  • Thursday, 5/18: Rhode Island first in English North America to ban slavery, 1652; Siege of Vicksburg begins, 1863; Mt. St. Helens primary eruption, 1980
  • Friday, 5/19: End of Mexican-American War, 1848; victorious Task Force 16 heads back to Pearl Harbor from Coral Sea, 1942; MLK’s Letter From Birmingham Jail published, 1963
  • Saturday, 5/20: Homestead Act signed, 1862; Lindbergh begins his Atlantic flight, 1927; Battle of Hamburger Hill ends, 1969

Today’s Birthdays: Vaccine inventor Edward Jenner, 1749; actors Dennis Hopper, 1936 and Bill Paxton, 1955; boxer Sugar Ray Leonard and comedian Bob Saget, 1956; musician Trent Reznor, 1965


Holidays Around the World: It’s Constitution day in both Norway and Nauru, while Norway also celebrates Children’s Day. Argentina observes Navy Day, and it’s World Hypertension Day and World Information Society Day. Go do something relaxing and keep your blood pressure down! 🙂

This Week In History is compiled with assistance from History.com and Wikipedia. Something interesting not listed here? Please share in the Comments section–this is an Audience Participation Encouraged featurette.

Gratuitous Gun Giveaways

*Note: FMG Publishing giveaways require you to provide an FFL dealer’s info at entry. Aero Precision giveaways give me one entry each per person who uses my referral link.

Quote of the Day

Inspired by the Feral Bureaucracy…
The illegal we do immediately. The unconstitutional takes a little longer.–Henry Kissinger


As always, the Watercooler is an Open Thread. The floor is yours for juicy gossip; in recognition of one of today’s birthdays I’m gonna go fire up my copy of Quake II (music by Reznor) and see if I can win the game using only the (Nine Inch?) Nailgun.

#NoQuarter #TheParty’sOver

By WarX, edited by Manuel Strehl (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
(Image by WarX, edited by Manuel Strehl at Wikimedia; used under Creative Commons Attribution license)


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