Will using a fabric moderator cover affect my rifle’s accuracy? Chris Parkin offers expert advice!

Q: I have seen people using fabric covers on their moderators. Will this affect accuracy, etc ?

CHRIS PARKIN replies: Moderator covers help minimise mirages interfering with the sight picture when your shot strings are longer. They can also be used to alter colours and shape slightly for camouflage reasons and lessen handling noise if knocked or bumped. The resonant sound harmonics might deaden slightly after the shot.

Some moderators do tend to zing a little bit without one. Anything attached to, or in contact with, a rifle barrel can alter the harmonics so re-zeroing it should be a matter of course if you add one. Secondly, if you change it, remove it, replace it or alter it in any way, you might need to check your zero again. If it is at all absorbent and gets wet, be sure to dry it thoroughly and don’t put it in your cabinet wet, as any additional moisture in this locked box is undesirable.

As for rimfire use, I think it’s a lot about looks, as many of the previous practical reasons are somewhat debatable. Looking deeper, ammunition is chosen or developed to a large extent based on the natural harmonics of your barrel/moderator. That is why some ammo suits certain barrels and not others and why we develop handloads that maximise performance for a particular bullet.

If you add anything and change that harmonic, you may find the consistency will change; you might need to redevelop loads or change your choice of factory ammunition if that occurs. Thankfully, life usually remains fairly straightforward, but just be aware of some of these potential pitfalls that can occasionally affect performance.