Does a choked barrel improve air rifle accuracy?
By B.B. Pelletier
Some airgun chat forums are currently buzzing with discussions about choked rifle barrels and what they can or cannot do. As usual, there are a few knowledgeable people and a much larger crowd of kibitzers with nothing to say - and saying it very loudly.
What is a choke?
A choked barrel refers to a reduction in the bore dimensions at the muzzle of the gun. The purpose for this reduction, according to pellet makers at Handler & Naterman (H&N), is to size all pellets just before they leave the gun. It ensures uniformity.
Chokes are more than a century old
Let's examine history to see if chokes really work. First we learn that Harry Pope, the acknowledged Stadivarius of rifle barrel makers, almost always choked his barrels. Most of the guns he made (and ALL of the most accurate ones) were muzzleloaders, and you might wonder how a choked muzzle can benefit a bullet that is rammed through it during the loading process. Wouldn't that squeeze it too small?
Well, when the powder charge ignites, burning gasses smack the base of the bullet hard, smashing it out fatter until it hugs every crevice of the bore. When it gets to the muzzle, the choke sizes it down once more just before it leaves the gun. Pope's barrels set every world record in their day; a century later, they're still regarded as some of the finest barrels ever made.
Lothar Walther chokes their barrels, too
A second endorsement comes from Lothar Walther, the German company that is well-known for making fine airgun barrels. They can supply their barrels with or without a choke, but their choked barrels out-shoot their unchoked barrels by a significant margin. They tell that to anyone who does business with them.
Now, a word from the school of hard knocks...
There are the incidents of hundreds of airgun tinkerers who have cut off the ends of their barrels for one reason or another. They nearly always suffer an accuracy loss that they can never recover. They will tell you the reason the shorter barrels don't shoot as accurately is because of the new crown (the shape and uniformity of the muzzle), but the truth is that no amount of re-crowning will ever get those barrels to shoot again. The one instance where cutting off the end of a barrel improves accuracy is when the muzzle has been ruined by improper cleaning that has worn away the rifling.
How to tell if you have a choke
Use a cleaning rod to push a pellet through your barrel from the breech to the muzzle. You'll feel resistance at about 1.5" to 2" from the muzzle on a deliberately choked barrel.
Pope lapped in his chokes during the polishing process. Modern barrel makers squeeze the bore down mechanically - a process known as swaging. On many springers, the act of swaging in the front sight dovetails on the outside of the barrel also reduces the bore at the muzzle. It isn't a formal choke, per se, but it works just the same.
The choke discussion is a topic that has fueled conversations for more than a century, and it isn't going to end here. An interesting book on the topic of accurate barrels is The Story of Pope's Barrels by Ray M. Smith.