As Jay mentioned check the barrel with a square and your best bet for a steel barrel is to look for a older Gamo in the Classifieds and use it for a donor, spare part. As far as the mainspring's go the springs are the same in the Gamo mid power shooters, ShadowSport, BigCat,Viper etc. etc. and not that their too powerful but taking the power on hand and taming it to be a smoother cycling airgun , tuning it. I have a Gamo Hunter Extreme.22 a Magnum airgun that shoot's great, got the mag power but it's power that doesn't jump the shooter out of your hands.Ed