Why airgun barrels can vary from one another

The subject of gun barrels and how they affect the accuracy of shots is something that shooters have taken a great deal of interest in since the early 16th century when people engraved the internals of a barrel to promote twist. Twist is what happens to our projectiles when they have engaged with the rifling, and allows our rapidly spinning load to stabilise and retain far more accuracy than if it was just sent on its way without any spin.

Apparently, the first person to use rifling in a manufactured firearm was August Kotter, an armourer from Nuremberg. He continued improving his work until 1520, with the first rifled-barrelled firearm dating from 1540. 

This did not mean all firearms were then produced with rifled barrels, as most were smoothbores. It wasn’t until the early years of the 1800s that rifled barrels started to become the norm. Even then, major conflicts such as the American Civil War (1861-1865) were fought with mostly smoothbore weapons, particularly early on in the conflict, with smoothbore muskets being far less accurate than the rifled weapons used later on that proved so effective at long range. 

This was also when the Minié ball first came about. This innovation with its expandable base allowed the bullet to fill the bore and produce more accuracy at longer ranges, which, when combined with decent rifled barrels, allowed shooters to take out targets accurately at even further distances.

These principles are still the way that firearms projectiles operate today, relying upon an explosive charge followed by a gas-tight round spinning its way up the barrel and out on its way to the target. Air-powered projectiles also very much rely upon spinning their way down the barrel before they whizz their way to the target.

For anybody who has been shooting for a long time, it quickly becomes apparent when they discover a gun with a good barrel. This will come about after purchasing either a new or used gun that displays the ability to drop pellets precisely where you want them in a nice tight group with few flyers. 

The problem is that from the outside, and even if we look inside at the rifling pattern, it is impossible to state whether an individual barrel will be able to produce the top line of accuracy required, particularly by serious target shooters. In essence, all that you see from a physical inspection is a tube of steel that possesses some cut rifling in the bore. 

Individual gun barrels produced by the same manufacturer, in the same factory using the same tools and materials will differ in their ability to perform downrange. 

There are many processes involved in cutting rifled barrels. The three diverse ways that the metal is either cut or hammered into shape are called broach, button and hammer-forged. 

By far the most popular method is the button rifling process, which involves pushing an extremely hard ‘button’ into the machined barrel under high pressure. This cuts and cleans the metal to the required profile, and is responsible for many of the barrels we find on our airguns. Apart from of course BSA, who continue to use hammer-forged barrels for their guns, produced within their own factory, and very good they are too!

Andy’s son James takes a shot with his Steyr, and in this case he had swapped the standard barrel with one from an Air Arms EV2

I don’t know about you, but I could count on only one hand the number of guns I have either owned or been associated with that have not had perfectly good barrels that once matched with their preferred type of pellet have performed perfectly. In fact, I can only think of one obvious lemon of a gun that I purchased new with a particularly bad barrel. It was a top-end German springer, and I was genuinely shocked when the gun would not perform to the levels I knew it should. In the end I moved it on as I just couldn’t get on with it.

I am sure that many of us would therefore love to know what it is that manufacturers do to produce a genuinely high-grade match-suitable barrel. I can only presume that the manufacturing process is very carefully monitored to ensure that only the best cutting implements or mandrels are used. Maybe if a tool is wearing out it will not be quite so effective at doing its job hundreds or possibly thousands of times before it is replaced on the production line.

Some companies do offer “selected” barrels for the rifle manufacturers wishing to purchase the ultimate in potential accuracy for their high-end target rifles. In my experience these barrels do tend to perform slightly better than their standard brethren, but sometimes they don’t!

As usual, in his endless search for shooting perfection out on the HFT course, my son James has recently been experimenting with different barrels on his Steyr target rifle. It must be said that the barrel provided by Steyr as standard on this LG110 was more than capable from new. Like me however, James has noticed that these particular barrels require a rigorous cleaning regime if they are to remain accurately zeroed. My own cleaning regime for the Steyr Challenge I currently own is to make sure that it receives a thorough pull-through following a maximum of 250 shots. 

The Air Arms-barrelled Steyr did well for James on the HFT circuit, with this performance earning him a high score of 59 ex 60

Any more than that might lead to some shots going astray. As James and most of his fellow HFT outdoor brethren will only get to shoot about 50-100 pellets per week according to how much practice they do, their barrel cleaning regimen is therefore something that happens every couple of weeks. This is unlike us indoor shooters who are often getting through up to 1,000 shots per week. 

As you can see, frequent shooting needs to equate to frequent barrel cleaning if our guns are to maintain their accuracy.

Having shot lots of pellets at a time for many years now, I can notice when the barrel starts to go ‘off’ and lose performance. As an interim method, very often I will use several barrel felts to at least tidy the barrel up before a full cleaning session when I get home. This often helps to bring the barrel back into its sweet spot, with normal accuracy being resumed with a reduced number of wayward shots.

The barrel that James is currently using is a Weihrauch barrel that has been machined to fit by Mick Tromans. This is currently performing well, although due to the additional length the power of the gun required turning down as a longer barrel can produce more power in a pre-charged pneumatic rifle.

Other barrels that were tried by James in his search for ultimate performance have included an Air Arms nickel EV2 barrel that also shot well, and a Steyr ‘barley twist’ barrel that all Steyrs were equipped with when they first became available here in the UK many years ago. 

This barrel possesses a highly polished finish that allows you to see the external grooves made during the manufacturing process. These barrels have achieved an almost legendary status amongst many within the outdoor target shooting fraternity for their perceived levels of superior performance over the years, although it would have to be said that many other barrels actually perform just as well if not better these days.

The bottom line with a gun barrel is to make sure that you find its preferred pellets and clean it more regularly than you do now. Guaranteed better performance!