What is the best weapon for a zombie apocalypse?

I love zombie movies, and books. I know that they are not real, but it is fun to think about it in a problem solving way.  I'm not much into vampires all of that erotic mambo-jumbo annoys me. Vampires are date nights gone wrong.  Since in the zombie  mythology all you have to do is shoot them in the head you need something that holds a lot of ammo and is quick to reload. Nothing really says anything about firepower, an arrow to the head works fine. I know, I know, we are not talking about man stoppers here, we are talking about zombie droppers. You do not need a 12 gauge slug to drop a zombie (or so I have read)  I'm going to go on the assumption that a .22 cal. round to the noggin of a walker would be enough to drop one of those bad boys. One problem you have with a firearm is sound, according to the myths if you shoot a zombie the noise will attract more zombie boys and girls and therein lies the power of zombie forces. They overwhelm you by swarming and by the weight of shear numbers they win. So, if we accept the idea that a .22 cal. round to the head will drop a zombie you need to decide which .22 gun is the right choice.  A revolver is too slow to reload, and at the most a .22 revolver will only hold 9  rounds so, cross it off. A .22 target semi-auto pistol is a step in the right direction, perfect for back up, quick to reload, most will hold about 10 rounds, some more, it is reliable, and accurate. And if you have a .22 rifle the major benefit is that both the pistol and rifle will shoot .22 LR (long rifle ammunition). You can carry a lot of .22 rounds, 500 of them only weigh a few pounds, and they are cheap and every gun or sporting goods store sells them.  Plus, in a zombie apocalypse you are more likely to fined them in a closet of an abandoned house. So, now what kind of .22 rifle?  A bolt action rifle is way too slow and it will only hold about 10 rounds.  You have the same problem if you use a lever action, you can load more rounds but it is too slow to reload. A perfect gun is the Colt or S&W .22LR built on an AR type frame. You can hold 30 rounds and you can reload fast.  I think I would use a Ruger 10/22. It has been around a very long time, extremely reliable, and it will hold 30 round after market magazines, although it comes with a 10 round mag.  They sell accessories galore such as tactical stocks, and it is very affordable, they even sell silencers for the rifle (you need a class 3 license for the silencers). So, if the shit really hit the fan would I stick to my story here and use a puny .22cal against a hoard of human meat eaters? Nope.  I would use a Rock River 5.62 (.223) Remington M4., and for my sidearm I would use a Browning Hi-Power 9mm. The main thing is you need a lot of rounds.  With a 5.62 any police station would have them, the same as gun stores, the round is common, and so is the 9mm. I think I would find a place such as a Costco and hold up there, but then again, so would a lot of people, I going to have to think about this one.  Let's hope it never happens.