There's so many people in this world has an extreme hobby such as shooting. those who has shooting as their hobby must be familiar with gun parts and the specification of the gun. several years before this stuff was only familiar on the military force but now those who have a shooting hobby can obtain this gun. You can find many high quality gun and it's parts on brownells dot com as the world's largest suppliers of Firearm accessories, gun parts and gunsmithing tools. beside sells a high quality guns, they also come up with books and video about Gun and weapons.
You can find a riffle parts, gun parts, automatic pistol parts and also shotgun parts and accessories on their website complete with the review of each products for an affordable price, for example is a Shotgun magazine extension, you can choose it on the product categories and read the review of it and also the rating on that shotgun parts. You can find further information on this AR15 Magazine.
With the easy navigation on their site it's not difficult to search your desired product because you can browse the products that you want based on manufacturer, if you're familiar enough with them.
How about the reloading supplies such as the bullets for your shotgun? don't worry you can also find it there. But please keep it on your mind before you buy all the gun accessories you have to ask your local authorities first because not all country allow a private gun and weapon ownership..