CZ 200T sounds like a trumpet

[Ranb]

I have two CZ 200T's for the smaller kids on the shooting team. One of them makes a sound like a trumpet, a loud blast of air, when fired. The rifle appears to be in good condition, it is several years old with a few thousand pellets through it, but has never been serviced by a gunsmith. The o-ring for the cylinder is in good condition.

My experience with repairing air guns is limited to replacing rings and seals on a FWB-65 and a FWB-300S. Is this something I dare take apart and look for something wrong?

Can anyone recommend a service and repair place in the USA? Thanks.

Ranb