Why won’t my new gun shoot straight!?

I’m at a loss as to why a gun I have just bought won’t shoot straight... what could I be missing? Chris Parkin replies

Q: I’m tearing my hair out trying to work out why a new gun I have bought will not shoot straight, and after all the regular jokes about my skills and usual checks have been performed, what else can there be to look at?

CHRIS PARKIN replies: The rifle that won’t shoot properly is not a rare occurrence in the shooting world but after the usual human error and mechanical checks have been performed and passed, I won’t deny, I have had a couple of serious head-scratchers.

The most obscure one was a small .17 rifle that, at first, I considered incapable in any kind of wind, but on its first calm test day, still acted like a fully choked .410 at even 50m. I investigated everything and my last chance was the barrel interior, which, due to its .17 calibre dimension, wouldn’t accept my borescope, although it had been ‘eyeballed’ endlessly. In the end, I was assessing the crown and although nothing seemed blatantly obvious, I happened to drop a bullet into the bore and found it pressed in easily for about 25mm. At first, just fingertip pressure was needed, after which a cotton bud got it in a full 50mm. It turned out that the button-rifled barrel was missing a good few thou off the lands in the rifling and what should have been a very tight fit (just ask anyone who has had to hammer a bullet out of a jammed bore) was actually slack. And although pressures and velocity were generated in the first 600mm of bore, those last few centimetres had gases bleeding out and past the bullet with it rattling loose before exiting the crown. That sounds dramatic but microns of movement are all that is needed before bullets toss and turn all over the place, and I was lucky enough that the bullet had enough stability to at least make circular holes in the paper of the target. Thankfully, a fault like this, although tricky to diagnose, is easy to cure and the manufacturer quickly replaced the rifle, accepting a genuine quality-control fault. You never know what good service is until you have a problem and this particular maker has a well-deserved reputation for accuracy and customer service which I will support. They accept and learn from their rare mistakes, rather than burying their heads in the sand, and that is how they became a huge name in the international gun world.