All things get dirty. Your rifle scope is no exception. Most people keep their scopes clean and shiny on the outside, but if one grabs a flashlight and starts peeking down the inner tube of the scope, chances are you will see some “dirt” on the side of the inner tube. In some extreme cases, these “dirt” can even be found on the reticle glass and make it visible during regular use of the scope.
How do you clean the inside of a rifle scope? It depends on where the “dirt” is found. If “dirt” is located on any of the glass elements (including on the reticle), you can simply grab your scope like a baton, and gently knock it a couple of times. Make sure you maintain a consistent force and hit only one direction. Repeat a few times if the “dirt” is still visible. If the “dirt” is found on the metal inner tube, there is no need to clean them because the oil applied to the inner tube will trap the dirt and prevent them from falling on to the glass elements.
Some of you might be concerned about knocking the rifle scope. Rest assured that your scope is built to withstand recoil, and a few gentle knocks should not bring any real damage. However, do pay attention to any sharp edges as it could scratch the body of the scope and leave undesirable marks.
Why there is “dirt” inside your scope
These “dirt” like particles are not dirt. If the riflescope is appropriately sealed, it is unlikely for dirt to get into the body of the rifle scope. Most of the time, these dirt like particles are tiny metal particles produced right inside the scope by wearing and tearing.
There are several moving parts inside your rifle scope. When you adjust your scope, these moving parts will get in contact with each other. Over time the metal on metal contact produces small particles. Most rifle scopes should have an oil-based lube on the inside of the scope tube, and this lube will attract the metal particles and keep them away from getting on to the lens elements or the reticle. But from time to time, the lube loses its stickiness, and some metal particles will get onto the lens or reticle.
Ways to Reduce Particles and Dust
Since these metal particles are usually produced when metal parts touch each other, the best way would be to limit the need to adjust the rifle scope once it is properly zeroed. This includes adjusting windage and elevation turret and parallax knob. However, the regular use of the rifle scope should not produce too much metal dust, and if they do, the inner tube lube should catch the metal dust with no problem.
If you find more and more dust accumulating under normal usage, it is recommended to begin your warranty claim as soon as possible. Most brands will honor their warranty for issues like this.