## Ballistic coefficient: What is it? Part 2

by Tom Gaylord
Writing as B.B. Pelletier

Part 1

This report covers:

• Review
• Today’s discussion
• Round balls
• Conical bullets
• Smokeless powder
• A big point
• Shape
• Round balls — again
• The bottom line

I’ve taken 11 months to return to this subject of ballistic coefficients (BC). That was in spite of some tremendous interest in Part 1 of this report last May.

I’m purposely avoiding all discussion of mathematics, which is difficult, since ballistics is a discipline that heavily employs mathematics. But I’m not qualified to write about the math; and, more importantly, I know that 99 percent of my readers would be turned off if I were to write the report that way.

### Review

Last time we learned that the BC of a pellet:

• Is an extremely small decimal fraction compared to the BC of a conical bullet.
• Varies with the velocity of the pellet.
• Varies with the shape (form) of the pellet.

## Ballistic coefficient: What is it? Part 1

by Tom Gaylord, a.k.a. B.B. Pelletier

• Definition of ballistic coefficient (BC).
• How are BCs determined?
• Bullets and pellets have an additional factor.
• BCs are not constants.
• BC is an expression of how much velocity is lost in flight.
• How to cheat the BC numbers.

If ever there was an elephant in a room full of airgunners — this is it! Ballistic coefficient. It seems like everybody talks about it, but what does it mean?

Definition
Ballistic coefficient (BC) is the measure of a ballistic projectile’s ability to overcome air resistance in flight. It’s stated as a decimal fraction smaller than one. When diabolo pellets are discussed, the BCs are very low numbers in the 0.010 to 0.045 range because diabolos are purposely designed to slow down in the air. Their wasp waists, flared skirts and hollow tails all contribute to very high drag that rapidly slows them down — much like a badminton birdie. Lead bullets, in contrast, have BCs between 0.150 and 0.450.

## Swaged bullets: Part 2

by Tom Gaylord, a.k.a. B.B. Pelletier

Part 1

This is the second report in this series on swaged bullets. My initial purpose for testing these bullets was to see if I could make a swaged bullet that would shoot more accurately than patched round balls in the rifle barrel of my Nelson Lewis combination gun. While testing that gun, I blew out the nipple and had to repair the gun before it would shoot again. Thankfully, that’s all done now; but I decided, instead, to use a Thompson Center muzzleloader in .32 caliber as the testbed for this idea.

When I first tested the swaged bullets at 50 yards, I couldn’t get a shot on the paper; so this past Monday, I shortened the shooting distance to 25 yards, in hopes I would be on paper. Since I’m reporting this now, you know that I was successful.

## Swaged bullets: Part 1

by Tom Gaylord, a.k.a. B.B. Pelletier

This is the start of a long exploration into the use of swaged bullets in both firearms and airguns. I told blog reader Robert of Arcade 2 days ago that I was about to start this one because he was talking about wanting to use the larger smallbore calibers (.22 and .25 calibers) and smaller big bore calibers (.257 and .308) to hunt larger game. But to do that, we need bullets (and pellets) that are accurate.

This report has been nearly one entire year in development, but you’re just hearing about it for the first time today. It all began with my Nelson Lewis combination gun that I have written about many times. Back in the first part of that report, I showed you some original bullet swages that came with the gun. The problem I have with these swages is their design. The bullet is swaged into the die, but then has to be tapped back out of that one-piece die, which is very inconvenient. It would be easier to get out if the die had a separate nose punch that could be taken off the die and the bullet tapped on through.

## Rifling twist-rate primer: Part 1

by Tom Gaylord, a.k.a. B.B. Pelletier

Recently, we have had a number of questions about rifling twist rates that were attached to the twist-rate report. These questions are extremely important to the understanding of how bullets and pellets are stabilized, so I’m starting a tutorial on rifling twists today. I’ll keep adding sections as I see the need to explain more about the topic.

Today, I want to lay a basic foundation of what the rifling twist rate does. Blog reader Feinwerk asked if centerfire rifles (he said higher-power firearm rifles) had different twist rates than rimfire rifles, and the answer is yes. I’ll get to that, but let me start at a time when things were much simpler.

## What about solid “pellets?” Part 1

by Tom Gaylord, a.k.a. B.B. Pelletier

The most refreshing thing about this blog is that we keep getting new readers, while retaining a large percentage of our long-time readers. That allows me the occasional opportunity to share an inside story with several hundred of my closest friends. Today is such an occasion.

We got this comment yesterday morning from reader Jp:

BB, got another question: You ever heard of using a solid pellet in an airgun. A bullet, I guess would be the correct term. Considering an airgun tends to shoot like lower velocity black powder (usually subsonic, I assume), maybe use something like a Minnie-ball shot. Know anything about this, how it works, how it doesn’t work, is it worthwhile or even a good idea? Jp

## Nelson Lewis combination gun: Part 4

by Tom Gaylord, a.k.a. B.B. Pelletier

Nelson Lewis combination gun is both a rifle and a shotgun.

It’s been a while since I last wrote about this gun. Blog reader Kevin asked if I was going to write anything more and I answered yes, but what I did not tell him or any of you was that in October of last year I blew up the gun.

Blew it up?
That’s not entirely accurate. What happened is the nipple that accepts the percussion cap was blown out of the barrel and right past my face. When it went, it sheared off the hammer lug that connects the exposed hammer to the sear. I never found the nipple, but the hammer was lying on the shooting bench next to the gun. When my shooting buddy, Otho, asked me if I was okay (he was standing behind me, having a premonition that something bad was about to occur), I answered, “NO” for the first time in my life. Usually, guys will say everything is okay right after they’ve sliced off their thumbs with a circular saw, but this event was so startling that I wasn’t really sure what my condition was. “No” just popped out.