ARP 031 - Feeding the Black Rifle | a Brief Look at Ammunition

Reed takes a look at the various 223 and 556 AR-15 ammo options.

Welcome to episode #31 of the AR15 Podcast.  I’m your host Reed Snyder and tonight I will be recording solo again. This is THEE podcast about your favorite black rifle! This show is for you; whether you're building your first AR or you’ve been building AR’s for years. There’s something we can all do to take our black rifle to the next level.

As many of you know, Otis has signed on to provide us with 3 months of weekly giveaways of their BONE tool and bottles of their O12 carbon remover.  Last week we announced the start of our giveaway contest.  Due to the timing of our podcast’s recording and posting schedules, we are going to announce the winner of our contest started with Episode 30 during Episode 32.  Meanwhile, keep sending your feedback to be considered for the next drawing to be held during Episode 33.   All you need to do to get a chance to be considered for a give away is to write in to the show at steve@ar15podcast.com or reed@ar15podcast.com.  Please visit Otis Technologies at www.otistec.com for all of your gun cleaning needs.  Make sure you tell them you heard about them from the AR15 podcast and the Firearms Radio Network!

AR-15 Training Tip of the Week:  

The fundamentals of marksmanship:

  • Aiming,
  • Breath control,
  • Trigger control, and
  • Follow through

Main Topic:

Origin of the Round:

  • .222 Remington
  • .222 Remington Magnum
  • .223 Remington
  • 5.56x45mm NATO

Variations of the 5.56mm:

  • M193 - 55gr ball cartridge
  • SS109 - 61 gr with steel penetrator
  • M855 - 62 gr with steel penetrator
  • M855A1 - 62gr lead free (19gr steel penetrator with copper alloy jacket)
  • Mk 262 Mod 1 77 gr SMK OT
  • Mk 318 Mod 0 62 gr OTM

Purpose Built Ammunition:

  • Hornady TAP  75gr
  • Mk 262 Mod 1 77 gr SMK OT
  • Mk 318 Mod 0 62 gr OTM

Listener Feedback:

Bob: Great job on the solo show this week. I just wanted to try and explain stress relief a bit better. At the normal working temperatures when drilling the bore or cutting the rifling you should not get up to a high enough temperature to harden the steel. In order to cause a phase change and harden you will need to heat the steel above about 1300=BA F. Quickly cooling from a temperature like that or higher will cause an extremely hard phase called martensite to form. That would need to be tempered back. When making the barrel especially cold hammer forged barrels will undergo cold-working. When you bend metal past the elastic region and permanently deform it you make it stronger. It has to do with forming dislocations and other complicated crystal stuff.  The more you deform the metal the stronger it gets. The stronger it gets it will lose ductility and toughness. You can restore the ductility and soften the metal by heating it up to a temperature below the original tempering temperature.

When I was going to school 13 years ago cryotreating was not very well understood. It would improve some wear properties. It was thought that it would remove retained austenite(a phase steel forms at high temperatures but is transformed during cooling). At the time it was one of those things that worked in some applications but they were not sure why. I don't know but I hope it is better understood now. We call metallurgy a science but there is still a lot of black magic and voodoo as I like to call it.

You also brought up using a 4340 steel. This would have a bunch more nickel than the usual 4140. With the small section size used in barrels the extra nickel is not going to help you that much compared to the cost. We use a 43XX series steel over a 41XX series for what we would consider thick sections. Something like a large 100 ton capacity hook that needs good through hardening.

iTunes Review:

Plate Carrier Giveaway:

Richard J from Benbrook, TX, is the winner of a brand new (with tag still attached) Condor Compact Plate Carrier in Coyote Tan courtesy of Brad from the FRN IT Team.

Outro: