September 18th, 2016

Why MVs Supplied with Factory Ammo May Be Unreliable

muzzle velocity applied Ballistics MV chronograph

Why You CANNOT Rely on the MV Printed on the Ammo Box!
When figuring out your come-ups with a ballistics solver or drop chart it’s “mission critical” to have an accurate muzzle velocity (MV). When shooting factory ammo, it’s tempting to use the manufacturer-provided MV which may be printed on the package. That’s not such a great idea says Bryan Litz of Applied Ballistics. Don’t rely on the MV on the box, Bryan advises — you should take out your chrono and run your own velocity tests. There are a number of reasons why the MV values on ammo packaging may be inaccurate. Below is a discussion of factory ammo MV from the Applied Ballistics Facebook Page.

Five Reasons You Cannot Trust the Velocity on a Box of Ammo:

1. You have no idea about the rifle used for the MV test.

2. You have no idea what atmospheric conditions were during testing, and yes it matters a lot.

3. You have no idea of the SD for the factory ammo, and how the manufacturer derived the MV from that SD. (Marketing plays a role here).

4. You have no idea of the precision and quality of chronograph(s) used for velocity testing.

5. You have no idea if the manufacturer used the raw velocity, or back-calculated the MV. The BC used to back track that data is also unknown.

1. The factory test rifle and your rifle are not the same. Aside from having a different chamber, and possibly barrel length some other things are important too like the barrel twist rate, and how much wear was in the barrel. Was it just recently cleaned, has it ever been cleaned? You simply don’t know anything about the rifle used in testing.

2. Temperature and Humidity conditions may be quite different (than during testing). Temperature has a physical effect on powder, which changes how it burns. Couple this with the fact that different powders can vary in temp-stability quite a bit. You just don’t know what the conditions at the time of testing were. Also a lot of factory ammunition is loaded with powder that is meter friendly. Meter friendly can often times be ball powder, which is less temperature stable than stick powder often times.

3. The ammo’s Standard Deviation (SD) is unknown. You will often notice that while MV is often listed on ammo packages, Standard Deviation (normally) is not. It is not uncommon for factory ammunition to have an SD of 18 or higher. Sometimes as high as 40+. As such is the nature of metering powder. With marketing in mind, did they pick the high, low, or average end of the SD? We really don’t know. You won’t either until you test it for yourself. For hand-loaded ammo, to be considered around 10 fps or less. Having a high SD is often the nature of metered powder and factory loads. The image below is from Modern Advancements in Long Range Shooting: Volume II.

muzzle velocity applied Ballistics MV chronograph

4. You don’t know how MV was measured. What chronograph system did the manufacturer use, and how did they back track to a muzzle velocity? A chronograph does not measure true velocity at the muzzle; it simply measures velocity at the location it is sitting. So you need to back-calculate the distance from the chrono to the end of the barrel. This calculation requires a semi-accurate BC. So whose BC was used to back track to the muzzle or did the manufacturer even do that? Did they simply print the numbers displayed by the chronograph? What kind of chronograph setup did they use? We know from our Lab Testing that not all chronographs are created equal. Without knowing what chronograph was used, you have no idea the quality of the measurement. See: Applied Ballistics Chronograph Chapter Excerpt.

5. The MV data may not be current. Does the manufacturer update that data for every lot? Or is it the same data from years ago? Some manufacturers rarely if ever re-test and update information. Some update it every lot (ABM Ammo is actually tested every single lot for 1% consistency). Without knowing this information, you could be using data for years ago.

CONCLUSION: Never use the printed MV off a box of ammo as anything more than a starting point, there are too many factors to account for. You must always either test for the MV with a chronograph, or use carefully obtained, live fire data. When you are using a Ballistic Solver such as the AB Apps or Devices integrated with AB, you need to know the MV to an accuracy down to 5 fps. The more reliable the MV number, the better your ballistics solutions.

Permalink Bullets, Brass, Ammo, Reloading 1 Comment »
September 18th, 2016

Eye Dominance and Marksmanship — What You Need to Know

6.5 Creedmoor Annealing

Shooting Sports USA Eye dominanceDo you know which one of your eyes is dominant? It’s easy to determine eye dominance with a simple exercise. Pick an object about 6-10 feet away (a light switch or door knob works well). Make an “OK” sign with your right hand (see photo) and hold that about 18″ from your face. Now, with both eyes open, look through the circle formed by your thumb and index finger. Center the circle on the object, so you can see the object in the middle.

Now, here’s the important part — while still holding your hand up, centered on the object, first close your right eye. If you don’t see the object anymore, then your right eye is dominant. If you still see the object, then repeat the procedure with the left eye shut and right eye open. If you don’t see the object when your left eye (only) is closed, then you are left-eye dominant.

6.5 Creedmoor AnnealingThe digital archives of Shooting Sports USA contain many interesting articles. A while back, Shooting Sports USA featured a “must-read” expert Symposium on Eye Dominance, as it affects both rifle and pistol shooting. No matter whether you have normal dominance (i.e. your dominant eye is on the same side as your dominant hand), or if you have cross-dominance, you’ll benefit by reading this excellent article. The physiology and science of eye dominance is explained by Dr. Norman Wong, a noted optometrist. In addition, expert advice is provided by champion shooters such as David Tubb, Lones Wigger, Dennis DeMille, Julie Golob, Jessie Harrison, and Phil Hemphill.

Top Rifle Champions Talk About Eye Dominance:

David Tubb — 11-Time National High Power Champion
I keep both eyes open, always. Some use an opaque blinder in rifle or shotgun shooting. If you close your non-dominant eye, you will not get as good a sight picture. If your aiming eye is not your dominant eye, you have even more of a problem to overcome.

Lones Wigger — World, National and Olympic Champion Rifleman
Shooters should try to use the dominant eye unless the vision is impaired and the non-dominant eye has better vision. You should always shoot with both eyes open since this will allow the shooting eye to function properly.

Dennis DeMille — National Service Rifle Champion
I close my non-shooting eye initially. Once I pick up my sight picture, it’s not something I focus on. For those that use a patch, I recommend that they use something white to block their view, rather than cover the eye.

Bruce Piatt — 2015 World Shooting Championship Winner
Some shooters, especially those with nearly equal or cross-dominance, will naturally find themselves squinting one eye. When anyone does this, you are also closing your dominant eye to some extent and adding stress to your face.

Permalink Optics, Shooting Skills 1 Comment »
September 18th, 2016

CGI Magic — 3D Animation of Pistol Rounds Being Fired

GECO Ruag Ammotec RWS ammo 3D animation video

Here’s a very cool 3D Animation showing pistol rounds being fired. Computer-generated graphics provide a look inside the cartridge at the moment of ignition as the primer fires and the flame front moves through the ignited powder. It’s really kind of mesmerizing. If you’ve every wondered just what happens inside your cartridges the moment that firing pin strikes, then watch this video…

Watch Video to See Handgun Ammo Being Chambered and Fired:

GECO Ruag Ammotec RWS ammo 3D animation videoThis animated video from German ammo-maker GECO (part of the Swiss RUAG group of companies) reveals the inside of a pistol cartridge, showing jacket, lead core, case, powder and primer. Employing advanced 3D rendering and computer graphics, the video shows an X-ray view of ammo being loaded in a handgun, feeding from a magazine.

Then it really gets interesting. At 1:32 – 1:50 you’ll see the firing pin strike the primer cup, the primer’s hot jet streaming through the flash-hole, and the powder igniting. Finally you can see the bullet as it moves down the barrel and spins its way to a target. This is a very nicely-produced video. If you’ve ever wondered what happens inside a cartridge when you pull the trigger, this video shows all. They say “a picture’s worth a thousand words”… well a 3D video is even better.

GECO Ruag Ammotec RWS ammo 3D animation video

GECO Ruag Ammotec RWS ammo 3D animation video

GECO Ruag Ammotec RWS ammo 3D animation video

Permalink - Videos, Handguns No Comments »