Clearing your throat

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Nigel, one of my regular fox shooting colleagues, is a good shot with his .243. We make a good double team, with me driving the pick-up and holding the lamp, and him on the back using a padded box on the cab roof for a shooting rest.

Over the years we have accounted for many foxes that way, and I’ve watched Nigel take some impressive shots at ranges of 200 yards, and beyond, when the conditions are right. I’m not keen on his light trigger, but he likes it and he can certainly do the business.

Nigel is particular about his kit, and regularly checks his gun’s zero. If you were being unkind you’d call him nitpicky, but that’s the rifle shooter’s mentality. His view is that rifle shooting is about placing a fast projectile onto a distant spot with pinpoint precision, despite all the external factors that conspire to mess things up. An attitude of ‘that’ll do’ just doesn’t cut it. That is why Nigel buys his ammo in batches of 300, shoots endless practice targets, and cleans his barrel painstakingly after every outing. He knows that if he allows three inches for windage and six for drop, it is an accurate measurement and not a lottery owing to group size. This instils confidence in the rifle and yourself.

Barrel bother: Nigel knows the cause of his off-target shots, but he now faces another dilemma

Barrel bother: Nigel knows the cause of his off-target shots, but he now faces another dilemma

So when Nigel told me recently that he was worried about his accuracy, I knew something was up. He told me his groups weren’t what they used to be – and he had the targets to prove it. He brought along a collection of targets shot over the past few years. As recently as November, his 100-yard groups were nicely within a one-inch circle. Some of them showed one shot off to the side, then two or three in the centre. ‘Sighters,’ he explained. He was that confident in the rifle, and in his shooting, that he would fire one shot then adjust the scope by the required number of clicks. Usually the following shots would be dead centre.

More recently he had found that one in every few shots one would fly off, hitting 1½-2in away from the rest of the group. At first he wondered about his own shooting – perhaps he had developed a flinch? He considered other factors: a bad batch of ammunition, a faulty scope or loose mounts, or perhaps a wobbly moderator.

We had a sneaking suspicion it was something else: a ‘shot out’ barrel, or more precisely a torn-out throat. When I asked Nigel about the age of his rifle, and how many shots it had fired, he did some sums and the results surprised us both. He worked out that he has owned the gun nearly 12 years and fired well over 3,500 rounds through it. It sounds a lot, but he shoots perhaps 200 deer and foxes a year as well as his regular zeroing and practice sessions. Multiply that up and there’s no escaping the fact that the barrel has seen a lot of use.

A Bisley competitor may consider changing barrels after 2,500 rounds; some of them replace the barrel at the end of each season regardless. My own foxing rifle, a .223, has been through a few barrels over the years.

Typically I would expect to see a barrel’s performance start to deteriorate after around 3,000 rounds, although I once watched a 600-metre ‘sudden death’ shoot-off won with a 7.62 that had fired 8,000 rounds. A chrome-lined mil-spec .223 barrel can last 40,000 or more in a bolt action.

The long and short of it: Bullet length can affect how your ammunition deals with wear

The long and short of it: Bullet length can affect how your ammunition deals with wear

Usually accuracy is lost owing to erosion in the throat, just where the bullet first engages the rifling. This spot takes the heaviest pounding from the hot gases exiting the case, and erosion is inevitable. The more powder burnt in a given barrel size, the faster the wear. Even with a relatively gentle round like the 100-grain .243 that Nigel shoots, eventually accuracy will suffer. Looking down the barrel and seeing good rifling doesn’t tell you the story of how worn that barrel is. As Nigel is religious in his barrel cleaning, the bore still looked good. Buyers of second-hand guns, take note: Always ask how many rounds have gone down the barrel and how worn the throat is. Wear can be visually checked by using an endoscope.

What happens is that the start of the rifling recedes down the barrel, and the throat erodes, so there’s a slowly widening gap that the bullet has to jump before it engages the rifling. With the barrel no longer holding the bullet tightly in line as it exits the case, it can tilt slightly before it sets into the rifling. It becomes unpredictable to start with, as sometimes it lines up and sometimes it doesn’t, and reliable accuracy begins to go out the window. As more wear takes place, eventually most of the bullets are out of line, and a shotgun pattern appears on the paper.

You can compensate for this, up to a point, if you homeload your ammo. I do it myself with my .223. As the rifling recedes, I load the bullet further out of the case, to maintain the ideal gap of about two thou’ (two-thousandths of an inch) before the bullet engages the rifling. (Don’t let the bullet rest in the rifling as it often raises breech pressures.)

The precise overall length of the cartridge depends on the bullet’s shape. A steep spire-point bullet will need to be out of the case more because of its long shoulder – the part that actually engages the rifling is quite far back from the point, compared to bullets that have a more rounded shape. Because of varying bullet lengths and different ogives, bullets can vary in their tolerance of wear in the throat. Sometimes a heavy bullet will continue to shoot fairly well long after a lighter one has thrown in the towel – because it’s shorter, it doesn’t jump the gap as well.

Cluster crisis: Stray shots can mess with your head and make you think twice about pulling the trigger

Cluster crisis: Stray shots can mess with your head and make you think twice about pulling the trigger

I proved my point to Nigel by loading a dummy round to the correct length for his worn barrel. I did this by knocking the primer out of an empty case while sizing the neck, putting a bullet well out in the case and chambering the round. When it’s extracted, you can see the rifling marks on the bullet. Measure the length of the rifling marks on the bullet, subtract that plus a couple of thou’ from the overall length of the round, and you’re there. In this case the gap was 3mm more than it should be, and the marks on the bullet did not show nice clean-cut rifling, but a rather scratchy surface.

Comparing my specially tailored round to Nigel’s usual factory loads, it was clear that the throat of his rifle was making his bullets jump a big gap. We went out to my zeroing range on the farm to fire a few test shots, which confirmed our suspicions. Nigel was shooting very well with his ‘back-up’ rifle, an almost identical Sako 75 – but in stainless. But try as I might, I couldn’t hold a tight group with the worn one.

That leaves Nigel with some decisions to make. A new rifle would most probably be cheaper, but he wants to keep his rifle if he can. After 12 years he is used to how it holds, and he has fitted a special butt pad so the recoil doesn’t aggravate an old neck injury. He could reload some ammo, but that would only put off the inevitable, and the rounds would be too long to fit down into the magazine.

The obvious answer is to have a new barrel fitted to the gun, so Nigel is looking round for a gunsmith to do the work. In the meantime our foxing trips can continue, with Nigel using his second Sako 75, even though he finds the scope on that one more suited to daytime work.

I am pleased we got to the bottom of Nigel’s deteriorating groups, and proved that it was simple wear and tear. It was eating away at his confidence – something that can quickly mess up your shooting, leading to hesitation and missed foxes, which we certainly don’t want.

Robert Bucknell

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