ARP 017 - Ballistics

Welcome to episode #17 of the AR15 Podcast. I’m your host Jake Challand with Co-host Reed Snyder. 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 ARs for years. There’s something we can all do to take our black rifle to the next level.

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Main Topic:


  • Internal ballistics (sometimes called interior ballistics): the study of the processes originally accelerating the projectile, for example the passage of a bullet through the barrel of a rifle
  • Transition ballistics (sometimes called intermediate ballistics): the study of the projectile's behavior when it leaves the barrel and the pressure behind the projectile is equalized.
  • External ballistics (sometimes called exterior ballistics): the study of the passage of the projectile through a medium, most commonly the air between firing tool and target.
  • Terminal ballistics: the study of the interaction of a projectile with its target, whether that be flesh (for a hunting bullet), steel (for an anti-tank round), or even furnace slag (for an industrial slag disruptor).

Listener Feedback:

Dug Harris: AR-15 Podcast question I recently purchased a BCM AR-15 .556, rifle length (20”). For some reason it has a problem cycling steel cased .223 ammo. It does great with brass. When I say problem, I mean problem as in it won\'t eject the case and strip the next round...ever.  What do you think the problem is?  Thanks much and love the Podcast.

Joe:  Next, magazine springs. In 30 years of competitive shooting, collecting and selling guns, and running a small gun company, I have never seen a magazine spring that was too \"weak\" to function.  I don't believe springs wear out from sitting in a loaded magazine and will only believe it when I actually see one! I've found magazines that were left loaded for over 50 years that function fine. I might believe a spring could take a set that might impair the feeding of the last one or two rounds in a hi-cap mag, but have not seen it. Gunshops make a good profit on springs so consider the motives...

Finally, you mentioned shooting your personal defense ammo every 6 months or so to get \"fresh ammo.\" Ammo ain't fruits and vegetables! I've shot ammo from the turn of the century that is fine and performs as it did the day manufactured. I've got lots of CMP surplus from the 50\'s that is great ammo. I even have a test running. I've got a case of Mauser ammo from WWII. No telling what it\'s storage condition was for the 60 years before I got it. Since I purchased it, it has been in the workshop at my hunting camp. The high temperatures are over 100, lows in the 20\'s and usually about 80% humidity. Three years ago the camp flooded and the ammo was under about 5 feet of water for 4 months. I was going to throw the ammo out, but decided to keep it; I guess it\'s my hoarding problem! I cleaned the sand and mud out of the case, but didn't take the cartridges out of the boxes. I\'m going to shoot a box every summer to see how long it functions - so far, it\'s fine.

Myles: With your recent conversation on Canadian gun laws I thought I would chime in on what firearms laws look like in another commonwealth country.  New Zealand has some of the most liberal gun laws in the world, but they still suck. Suppressors are commonly available for as little as 50 NZ$. It\'s almost as easy to get Chinese M-14s, SKSs HK SL8s and AKs. The gun registry was done away with, if you want to legally own a firearm you need a permit of some sort, but they are fairly easy to get. However if you want an AR-15 there is only one option I know of, Bushmaster imports some ARs but they are TERRIBLE. They are so neutered that they make California compliant rifles look like a weapon of mass destruction.

Pistols are very tightly restricted, there is no legal CCW. To get a pistol permit you have to re qualify with your weapon once a month on a police range. Also I would imagine that shooting an intruder in your home, even one with murderous intent is a no no. Because you know all life is precious, even the lives of murders and rapists.

Illegal use of a firearm is a very bad idea because the country is so small that there is about an 87% chance that if you are firing off of a designated range you will be ratted out and the police will set up a cordon and swoop down on you. There have been several cases of this sort of thing happening over the past few years.

One more nutty note, in New Zealand you can legally own fully operational machine guns, mortars and automatic cannon under a collectors license. About a year ago a shop in Christchurch was advertising that they were selling 30MM antiaircraft cannon and MG34 machine guns for about 7,500 NZ$. Boasting about how a similar gun in the US would cost significantly more than that. Just one caveat though, if you own a machine weapon or an artillery piece you have to promise to never ever use it!

Bryan Bramley: Hi Jake, I've been listening to your podcast  since January and I really enjoy it. I appreciate you and Reed taking the time to put it together. I have a Rock River Arms LAR-8 (.308), Smith and Wesson M&P15, ISSC MSR (Resembles a SCAR) .22lr, and a Taurus 9mm... But who wants to talk about pistols, haha. Just wanted to say hey and thank you for a great podcast. Also, can I please be added to the running for all the great products you give away? Please let me know if there is somewhere I can sign up, thanks again!

John:  I have been enjoying the podcast so much since I am in the process of building my own. If only the parts were available. But oh well, in time. Eventually I want to build a 300 Blackout upper. That cartridge seems so interesting and fun. Well anyway keep up the great work.

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