Shopping Search is where it starts
It is apparent when you try and run a "Shopping Search" on Google.
If you type in any gun name, the only results you get back are for parts and holsters, not a single hit for buds, cheaperthandirt, or any other firearms retailer.
Or try and run a shopping search for "9mm 115 grain" - not a single result that is actually cartridges. Just a bunch of jewelry made from cases and watch bands.
Google's position is anti-gun. For now, their belief in the 1st Amendment is outweighing their dislike for the 2nd Amendment and they have said they will not censor web searches, but they will certainly not make it easier for you to buy things related to firearms. Bing (to my knowledge), still allows for shopping searches for guns.