Gamo Hunter Extreme in .177 calibre, opinions.

[Person NotWanted]

I am looking into a Gamo Hunter Extreme in .177 calibre (on hand in a local store) and have done some online research. I would like to ask for opinions of it from people who have had the opportunity to work with it. This is the first air rile I would be acquiring if I get it. I have fired a different air rifle in the past, although it was some time ago and I think it was just a <500fps model.
Also, can hinge action air rifles be changed to a different calibre by changing the barrel out? I assume that the chamber is just a groove at the inside end of the barrel, so it would be changed with the barrel.
If someone has experience with the difference between the .177 model and the .22 or .25 model of the Hunter Extreme I would also like to hear about those experiences. Thank you.

 

[Corntonio]

I have a Gamo Nitro .177. i bought it through Airgun Source in Ontario. At the time, it had to be registered as it was over 1000 fps. I have not looked into changing the barrel to .22 but, as many of these are offered in both calibres, it might be possible. check with Gamo. After 7 years it still destroys rodents quite well.