In this video I try to solve some accuracy issues with my Reximex Pretensis. It had been shooting really well, but after a morning shoot, things didn't seem to shoot as well as they should. Pellets that used to shoot well didn't.
I tested the rifle with six different pellets to see which worked best. This was done through a multi shot JCE magazine and a single shot loader from Bob Pattenden. Normally when pellets loose accuracy a good barrel clean solves the problem. I gave the barrel a good pull through, and re tested. With things improving, but not by enough, I changed the silencer. With accuracy still not what it should have been for most. (Bisley Magnum & Webley Accupell, shot well) Air Arms DF, H&N FTT, H&N Terminator, Excite Econ 2, Spitfires, not shooting good at all, through the multi shot magazine, I then tested them through Bob Pattenden's single shot loader. This gave a massive improvement, and showed that apart from Bisley Magnum and Webley Accupell, the multi shot magazine, pellet combination, didn't work with the other pellets. Through the single shot loader the Spitfires gave a particularly good account of themselves.

Other things to try when accuracy drops off is, check the crown of the barrel for damage. Check that the stock screws are not loose, and that the scope is tight enough. Check pellets for damaged skirts, and check that the pellets are not being damaged when being fed into the breach with the pellet probe.

Another factor that can affect accuracy is the weather, which normally is upset by high winds.