ARP 128 - Building an AR-15 from Scratch - Part 6


Welcome to Episode #128 of the AR15 Podcast. Parts 1 through 5 of our Building an AR-15 from Scratch series have left us with a complete, functioning rifle. Now it’s time to make sure everything is safe and working right.

Remember Brownells helps make this show possible.

Main Topic:  Building an AR-15 from Scratch - Part 6

Function Testing and Zeroing:  Prepping For the Range

Function Test:

  1. Mag release
  2. Bolt function
  3. Trigger function


  1. Decide on the Zero Distance
  2. Bore Sight the Rifle
  3. Zero the Rifle in small increments

Otis Technology:

May 11: Len Dichtel (dick-tell)

May 18: @spillicious

May 25: @msr300blk

June 1:  Billy W. - @bigbiller on Instagram

June 8: Chris Inouye

The fine folks at Otis Technology have sent over a mountain of rifle maintenance tools and cleaning kits for the AR-15 and AR-10.  We’ve been tasked with giving them away.  Watch for the special posts on Facebook and Instagram to get a chance to win some of the awesome products made by Otis Technology.  We’ll give away a complete MSR Cleaning kit in either 5.56 or 7.62 in the middle of eachmonth up until Christmas, when we’ll give away a complete Otis Technology Elite Cleaning System to one lucky listener.  During the alternating weeks, we’ll be giving away a host of Otis tools and cleaning supplies.


dan v: Hey guys...I just got a dedicated 22lr upper by Chiappa and put it on my standard bushmaster lower.  I took it to the range and ran cci ar tactical 22lr's.  It ran like a dream.  Any 22 platform will have a snag or two, but in 300 rounds I maybe had 3 issues...that\'s a 100:1 ratio.  I loved it and got some great range time in with my ar. Buds had the upper and 2 30 rd mags for about $130 on sale.  Best money I spent in quite a while. Ken from Phoenix: Thanks for getting the links to old podcasts fixed.  Episode 25 & Episode 13 are the only two that no longer have any active mp3 or youtube videos associated with them. In a past episode you asked, if anyone would be interested in purchasing the old episodes, on a memory stick or such.   An electronic download would be easier on you, you would not have to mail out each episode.  I would purchase if the price was under $40.  Prefer $20. You asked about the .458 SOCOM and the .450 bushmaster.   I have the 450 bushmaster.  There is a forum for the 450 bushmaster that the original designer frequents.  It is I choose the 450 bushmaster because I got a good deal on it.   I have used it to hunt Elk.


  1. In episode 125 you missed a wonderful opportunity to plug Brownells’ rifle builder function on their site. I think uppers are where I have the most questions about "will this and this work together" and the tool on their site is a great help.
  1. Building an AR-15 from Scratch - SBR Edition. Discussion of barrel lengths, gas system lengths, tuning the gas system, handguard length and diameter, muzzle devices, etc... Also, I'd love to hear JW on this particular show; if memory serves, he missed the last SBR show.
  1. Building an AR-15 from Scratch - Precision Rifle Edition Longer gas systems Tools for improving accuracy such as the upper lapping tool mentioned in episode 125 Triggers Optics Optics mounts Hand guard Bipods/ monopods

Michael from Burlington Connecticut: Question-- I wonder if you could speak on barrel selection. Specifically selecting the right feed ramps to match your upper and what are the different barrel profiles available and what benefits do they offer. Additional info: For example m4 profile, A2, socom, midweight, lightweight? And for reference the upper I am building is on a Diemaco A1 upper, no feedramps. I'm enjoying the build podcasts. I have built lowers but never an upper. I'm assembling parts for a short barreled, A1 lightweight upper. Israeli defense force inspired.