The Hatsan model 25 is a air pistol. Don't know with what purpose you'll be buying it, but rather restricted in the UK version (max 6 fpe) Rather hard to cock, to keep steady and to hit something regular. It's really a beast of a very hard-hitting air pistol ( Dutch version doing 11+ fpe ) You could look for the Model 25 tactical (supertact), which has a integrated shoulderstock, which makes it easier to aim a bit more steadier, but fixing a scope isn't easy either.(don't know if these are classified as a airrifle in the UK ?)
http://www.hatsan.com.tr/en_mod_25_supercharger.html
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