IR
I was asking a similar question not too long ago, just before I picked up one of the 440's from Natchez. Most answers ran along the line, that most Gamo power plants are the same. I also did a little more looking since then and looking at Gamo.com not GamoUSA.com My guess is they have two basic levels of power plants. Standard power and high power and possibly the hunter extremes are different, they look different, don't know. I believe you are mostly paying for upgrades in appearance and accessories, polymer stocks, wood stocks from plane to some checkering to checkering front and rear and the accessories, a wide assortment of sights and scopes. The only big upgrade they don't offer that needs to be there is a good trigger. But CDT can fix that part immediately with the GRTIII trigger. I have a Hunter Elite and the 440 they look different and are accessorized differently but the way they shoot, both with GRTIII triggers is very similar. I like Gamo products, and would recommend them to friends, and with a little work, mine have both turned out to be very nice.
W