I have a Big Cat . The O-ring seal located on the compression tube side not the barrel needs to be replaced. The bolt that locks up the barrel was about 1/16 too long and damaged the seal on closing the barrel.
Does this use the Gamo Medium seal that they sell? Also what is the best way to remove the old seal and replace with a new seal without going insane???
I have since carefully removed just enough of the bolt projection to avoid the seal. I was surprised to see that it is plastic like most of the AG.