Learn about firearms to know more about airguns

by Harley Ayre

I got a question last week from a Danish airgunner who had to provide the government with the muzzle energy and energy remaining at 100 yards for his .50 caliber big bore airgun. It seems that is a requirement before one can hunt with an airgun in Denmark.

The answer seemed so easy to me that I wondered why anyone needed to ask. And then I thought more about it. The reason this airgunner didn't know how to find the answer is he doesn't know about firearms! So today I want to talk about how firearms and airguns are alike.

Bullets are bullets
This shooter referred to his 250-grain round-nosed bullets as pellets. He did so because when he bought them that's what the dealer called them. And they were going to be fired in an air rifle, after all. Guys, a bullet is a bullet, no matter what name you give it, and knowing that it's a bullet allowed me to calculate his required ballistic data. Looking in Sam Fadala's Blackpowder Loading Manual, Sam actually chrongraphed bullets from muzzleloaders at the muzzle and agin at 100 yards, using two different chronographs. His data is more exact than a calculation using a ballistic coefficient.

I learned that a 260-grain .50 caliber conical bullet retains 83 percent of its initial velocity at 100 yards and a 177-grain .490" round ball retains 60 percent of its initial velocity at 100 yards. So a 250-grain lead conical bullet should retain at least 80 percent of its initial velocity at 100 yards. All he has to do is calculate what level of energy that would give him and he's done. See how easy that was? Think the Danish government will set up a test range to prove him wrong? I doubt it.

If you are fuzzy about energy calculations, I will show you how that's done in the next posting.

Now let's carry this thing farther. A ball is a ball, regardless of its size, as long as the material it is composed of remains the same. So we can extrapolate the velocity retention for a .177 or a .22 caliber lead ball to the same 60 percent velocity retention at 100 yards. The ENERGY will fall to less than half, but that's easy to calculate, too.

Pellets are like some shotgun slugs
Some shotgun slugs are made with a hollow base to slow them down rapidly. Certain eastern states like the fact that the maximum distance these powerful projectiles will travel from a shotgun is around 800 yards. In the pellet gun world, we have the diabolo pellet that is even better at slowing down. A combination of a deep hollow skirt and a wasp waist makes the modern pellet slow down completely after about 500 yards. That doesn't mean with the rifle held level - it means with the axis of the bore inclined 30 degrees above the horizon, which the U.S. Army has determined to be the approximate inclination required to allow a ballistic projectile to travel the maximum distance.

Solid "pellets" are actually bullets
And here is what this all means. Put a 28-grain Eun Jin diabolo PELLET in an AirForce Condor set on maximum power and incline the axis of the bore 30 degrees above the horizon and the pellet falls to earth at 500 yards. Put a 30-grain solid BULLET in a Condor and do the same thing and the bullet falls to earth farther than 1,760 yards, which is one mile. Solid "pellets" turn a powerful airgun like the Condor into a rimfire rifle.

There is much to be learned by studying firearms. The ballistics all apply, plus many of an airgunner's deepest mysteries have already been resolved.

What is a choked barrel (...and why do we care?)

by Harley Ayre

Most shooters know what a choke does for a shotgun barrel. It constricts the shot column just before it leaves the muzzle, resulting in a tighter pattern downrange. A choked rifle barrel does the same thing, but not for the same reason.

What is a choked rifle barrel?
A choked barrel is a constriction in the bore size near the muzzle. Instead of a screw-in device or an add-on appliance, the rifle bore is made that way. The bore actually gets smaller. It is always a small amount - usually less than one-thousandth of an inch. Both the bore and the lands close in by an equal amount. This is done gradually to not disturb the bullet, or, in our case, the pellet.

Choked barrels are not new
Barrelmakers were choking barrels in the 19th century. Harry Pope, the most famous barrelmaker who ever lived, sometimes bored his choke along the entire length of the bore! I doubt anyone is still doing something like that, but isn't it fascinating that anyone would? Remember, he then had to lap (polish) the bore and then rifle it! Most barrelmakers lap AFTER rifling, but Pope did it both before and after! That's why a gun with a Pope barrel commands the price of a new luxury car today.

What does a choke do?
A choke assures the uniformity of the bullet/pellet at the most critical point in its internal travel - just before it leaves the muzzle. It actually swages (squeezes) the projectile slightly smaller, ensuring that all of them leave the bore a uniform size. This is the reason that it does very little good to run pellets through a sizing die. The barrel itself IS it's own sizing die!

The choke doesn't even have to be uniform!
It's true. The Weihrauch company builds a lot of spring-piston air rifles. They do not choke their barrels, but they do swage in dovetails to hold the front sight base. The upsetting of the outside of the barrel carries through to the bore, which becomes slightly choked. It may not sound like much, but let's look at what it does.

A little knowledge is a dangerous thing!
Back in the 1990s, when the internet chat forums were getting started, some people posted that the optimum length for a spring rifle barrel is 9-12 inches. After that, the pellet no longer accelerates. That's actually true, but what that fact did was start a rash of barrel-bobbing. Unfortunately, the barrel-cutters didn't get any MORE velocity, but they did manage to remove their chokes. So, they got less accuracy. If you shop for used spring air rifles, beware of "carbines" that are homemade!

Keepa you hands off!
Now don't run out and start damaging all your barrels in an attempt to choke them. If you have quality guns Like Falcons and AirForce rifles, the barrels are already choked correctly. If you push a pellet from the breech to the muzzle, you will actually feel the choke as it resists the pellet's passage. However, now you have another reason to not clean a barrel from the muzzle unless there is no other way.