https://www.hampshire.police.uk/ar/applyregister/fao/af/apply-firearm-shotgun-explosives-certificate/

https://www.nsra.co.uk/

https://www.nsrashop.co.uk/

https://nra.org.uk/home-page/

https://nra.org.uk/nra-bisley/ 

Recommended Reading

https://www.amazon.com/Art-Rifle-Jeff-Cooper/dp/1581605927https://www.amazon.co.uk/Art-Rifle-Jeff-Cooper/dp/1581605927/ref=sr_1_2?keywords=art+of+the+rifle&qid=1570179185&s=books&sr=1-2