Stringing It Out

Andy McLachlan explains how a scientific approach to a gun’s performance can locate the reason for the odd wayward shot.

Jimmy O’Neil takes aim at a standard 25-yard benchrest card – the bull is a minuscule 2mm

I am sure that many readers will have experienced disappointment as frequently as I have when it comes to putting in a run of good scores with an air rifle.

It is an often used comment that ‘we have never had it so good’ – regarding the ability of our guns to be super-accurate – and just as importantly, consistent – when we compete in either outdoors or indoors competitions.

As those of us who use airguns regularly for any purpose will be aware, the selection of the ammunition that best suits any individual gun’s barrel can only be achieved following much experimentation, unless you are lucky and discover the particular brand and batch number early on in your accuracy testing regime.

However you achieve this barrel/best pellet partnership does not really matter if you are confident that the combination will perform where you want it to – downrange at the target.

Once this barrel and pellet partnership has been discovered, the sensible shooter who’s able to afford to do so will then buy as many pellets of their preferred batch as possible to ensure that they do not run out halfway through a competition series.

There is nothing worse than discovering your ‘wonder pellet’ stocks are coming to a swift end and that you can no longer find anywhere to buy that precise batch of pellet.

The serious shooter will then need to consider a regular regime for cleaning their gun’s barrel. It is no good to have a previously superb performer suddenly ‘go off’ during a competition due to something as relatively easy to manage as barrel cleaning, and this can indeed be the root cause of bad accuracy.

Jimmy shoots a string over the chronograph and makes a note of each of the results

Very often, shooters will decide upon a pull-through of the barrel following the gun’s consumption of a tin of pellets for example, although one of my own guns requires a barrel clean every week to maintain its laser-like abilities.

The problem is that each gun barrel is unique. They might look the same, but if we are intending to get the best out of them, we need to once again experiment regarding the number of shots that an individual barrel cycles prior to being given the pull-through treatment.

We can usually discover at which point the barrel is starting to get excessively dirty when we notice the occasional pellet landing well away from the centre of any group.

If the pellets have been weighed and visibly checked for optimum results, we can usually be sure that a cleaning of the barrel at that point will resolve the issue, well hopefully!

In a perfect world, a cleaning of the barrel will once again result in deadly accuracy. The problem is of course that it very often doesn’t resolve those annoying ‘flyers’, when the odd shot lands nowhere near the intended point of aim. This might be anything from just a few millimetres away from hitting the bull to a few centimetres in particularly bad cases.

Additional problems can occasionally occur when the shooter is confident that they are using the best ammunition for their barrel and that this is in good condition, following regular or even additional cleaning. This is when serious shooters start to consider additional considerations such as how the gun’s action is performing.

A significant change in velocity is a sign there’s a problem, but this gun was absolutely fine

Although there are many excellent rifles out there that shoot perfectly well without a regulator managing the precise delivery of air pressure behind the pellet, it would have to be said that all ‘serious’ (usually expensive) guns will possess a regulator.

This device, via the use of an additional chamber, allows a series of sprung Belville washers to maintain a chosen pressure of air to be delivered consistently to the rear of the pellet.

The regulator can be adjusted up and down to modify the output pressure delivered to the pellet, with good examples of regulators able to deliver consistent velocity readings of less than five feet per second on occasion, or some even lower than that.

In addition, considerations such as hammer tension need to be considered when attempting to find the perfect balance for a particular gun’s preferred firing cycle at any given velocity reading.

If the hammer spring has been adjusted so that it hits the main firing valve with a wallop, this might even result in the valve ‘bouncing’, resulting in additional supplies of air being wasted from the individual firing cycle.

An agreeable balance between regular pressure and hammer spring tension is a major consideration for those individuals wishing to set up their guns for optimum levels of performance.

As I mentioned in another article recently, the best people to set up guns to shoot at their optimum levels are those with the experience needed to initially experiment themselves prior to any adjustments being made to the original manufacturer’s settings.

Let’s face it, the companies that make our guns have a pretty good idea just what is required for the average shot and will set up newly manufactured products to suit the present legal power requirements.

An example of how a serious target shooter, in this case benchrest, attempts to identify the main cause of the occasional wayward shot is here described. My friend Jimmy O’Neil is a confirmed benchrest target shooter that takes his sport very seriously. Shooting at 2mm targets at 25-yard benchrest cards swiftly identifies any accuracy issues inherent within any gun.

The gun in question was an Air Arms HFT 500. This gun is a known performer straight out of the factory and has earned its spurs both outdoors for HFT and for indoor benchrest competition.

Jimmy takes his sport seriously, owning both an HFT 500 and a Rapid Air Weapons TM 1000

One of our mutual friends, ‘Woki’, following a recent rest and recuperation period from flying the Millennium Falcon around and about the Galaxy, has been maximising the performance of this particular model of gun, and fitted a Lane regulator free of charge to some close friends’ HFT 500s recently.

Due to Woki’s efforts and the added shot-to-shot consistency available following the fitment of a regulator to the HFT 500 action, the gun performed, according to Jimmy, as well as, if not better than, his Air Arms FTP900 and Rapid Air Weapons TM 1000, both of which feature regulators as standard.

Jimmy was more than happy with the ability of the 500 to score highly downrange, but he started to notice the very odd wayward shot failing to take out the centre of the 2mm bull.

Being an experienced shot, Jimmy firstly checked his ammunition and the cleanliness of the HFT 500’s barrel which were found to be perfect. He then decided to run a full charge of shots through a camera bipod-mounted chronograph while his rifle was fully supported and shooting at a regular 25-yard card. This allowed him to establish any shots that failed to take out the bull and the velocity of each one, which was recorded in his notebook.

Jimmy experiments with head positioning by moving his cheekpiece forward and back to find the optimum

As a result of these investigations, Jimmy discovered that the Woki-fettled and Rob Lane-regulated HFT 500 remained perfectly consistent throughout its charge. In other words, the gun was performing perfectly!

This led Jimmy to discover that very occasionally he wasn’t positioning his head in the same position for every shot, meaning that any misses were due to our old enemy parallax error. Jimmy then fitted a line of tape upon the top of the stock’s cheekpiece to ensure perfect noggin position every time.

This resulted in a problem solved in this case due to a scientific approach to identifying any actual or perceived faults with a gun. Jimmy, using this HFT 500, has recently recorded his personal best benchrest score of 250 with 23 Xs. Many times, it is us either imagining a fault or blaming our equipment if we can’t hit that target every time. Usually it’s just ourselves that we need to take a close look at – which means that we need to leave those guns alone

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