Why has my rifle suddenly become inaccurate?

A: Some problems can be complex to diagnose but others are simple and can be rectified at home. Barrel fouling or damage to the muzzle of the rifle can cause these problems, but sometimes a dried piece of dirt pressing against the barrel, changing the barrel harmonics on ring, or dirt in the bedding of the action will cause inaccuracies suddenly. It is also worth checking that the bolt shroud or bolt handle are not touching the stock. The way the bolt is locked and supported makes a big difference to the way the rifle vibrates when firing, which ultimately affects the accuracy of your rifle.

Could it be moisture?

Moisture can swell a wooden stock or grit can get into a synthetic one that will alter the bolt position. Check that the bolt shroud at the back of the bolt body is not touching the stock, as any adverse pressure will cause erratic shots. Also check that the bolt handle is not interfering with the stock when closed and that it locks down fully. It is simple to rectify the above by filing down any excess wood or synthetic material where it touches with sandpaper or a small file.