I purchased a wildcat sound mod yesterday for my t3 243. After talking to the lad in the gun shop, he mentioned drilling the cap that goes on the end of the mod over the barrel (if you know what I mean).
Basically he advised me to either drill it so it was very tight or drill it so it had plenty of clearance around the cap and the barrel. Apparently if its not tight it can effect the harmonics of the barrel. He went on to tell me that most people just leave the cap off.
I dont want to leave the cap off because personally I think its asking for problems later on with dirt etc.
Just wanted to know how you've fitted yours and whether it does actually make a difference.