by B.B. Pelletier

This experiment came at the request of Pyramyd Air. They noticed that people on the chat forums were saying that a shrouded barrel made a gun more accurate, and they asked me what I thought. I thought (and still think) that a barrel shroud has little or nothing to do with accuracy, but I said I would try an experiment to see what happened.

Talon SS
Since the Talon SS has the prototypical shrouded barrel and is the rifle that gave all the other makers the idea for shrouding in the first place, I decided to use it for the test. All I had to do was remove the muzzle cap to shoot the gun without the effects of the shroud – or so I thought. I used 50 yards as the range because the SS is so accurate that anything closer might not show a difference.

First – with the end cap installed
My SS is .22 and shoots JSB Exacts best. The first group of five measured 0.599″ between the centers of the two widest shots. The next group was a carbon copy of the first – another 0.599″ – but I had adjusted it to the center of the bull. Those two groups proved the rifle was shooting well, so I removed the muzzle cap.


A nickel will cover the 50-yard group of 5 JSB Exacts made by the Talon SS with the muzzle cap on.

With the end cap missing
The next group began like the previous two, with pellet holes touching. Then shot four went wide to the left. Shot five went to the right of the initial group, opening it up to 1.117″. I was surprised but figured it was a fluke, so I settled down and shot another group. This one was even more open, at 1.182″. I was very discouraged after this group because there were only three holes in the target. Four of the pellets went into the same two holes, but those holes were far apart!


Take the cap off, however, and the story is different! Shots are blown all over the place.

End cap reinstalled
I put the end cap back and shot a group measuring 0.820″. It was larger than the first two but back on the good side of the inch mark.


The chamber of the Talon SS may focus the muzzle blast back into the pellet’s path.

Conclusion
If you remove the end cap from a Talon SS, your groups will get bigger. I don’t think this proves that shrouded barrels are more accurate, because the plain Talon barrel that has no shroud is just as accurate as the shrouded SS. What I think this experiment demonstrates is that the muzzle blast can affect accuracy if it isn’t permitted to escape. With the cap off, the deeply recessed muzzle spews air against the wall of the receiver, where it rebounds against the pellet for the first four inches of flight. With the cap in place, the same air is prevented from following the pellet through the hole in the cap. What happens in the chamber before the pellet emerges through the hole in the cap apparently does not have any lasting effect.