The best gun for combating the undead depends on how long you actually survive the zombie apocalypse.
Ever since the zombie craze of the 2010s hit the world, heralded by films including 28 Days Later and the remake of Dawn of the Dead, plus the shocking popularity of The Walking Dead on the small screen, gun people have wondered what the best weapon for zombie fighting would be if something similar were ever to go down in real life.
I've spent plenty of time shouting at the morons on The Walking Dead, who see others use melee weapons like swords and knives to great effect, but can't manage to make use of a single spear. Instead they endeavor to reload .223 ammo with homemade gunpowder instead. Did they ever get an ammo plant up running? I don't know, I stopped watching a good while ago.
The deal with the most recent incarnations of zombies is that they can take any abuse and punishment to their bodies that can be dished out, and their jaws will keep snapping. To kill them once and for all requires brain trauma. So, that means headshots. But outside of the world of TV and Xbox video games, headshots ain't so easy.
With this caveat in mind, let's look at our options.
Eye on the target.An #ArmyTeam Soldier assigned to the 42nd Military Police Brigade fires an M4 carbine rifle during the M4 qualification event on Joint Base Lewis-McChord. [Photo by Sgt. Jasmine Higgins]
An assault rifle is a pretty solid choice for zombie fighting. You have large magazine capacities with fast reloads, and with iron sights or a variable zoom optic, they're capable of precision shooting at range.
If you get your hands on a discarded military issued assault rifle after the collapse of society, you can engage a small horde of zombies at close range with three-round burst fire. If you aim at head level, you could take out several at once.
A good M4 Carbine, or pretty much any AR-15 variant, would be a solid choice here. You will be able to find 5.56/.223 ammo most readily. The next choice would be an AR-10.
Of course, as time passes and ammunition becomes more and more scarce, rifle rounds are tough to reload without the proper components and tools. Primers, powder that burns at the correct speed, and jacketed bullets necessary for cycling a semi-auto would all be tough to come by, as well as brass casings themselves.
Bolt action rifles run into the same issues, but lever action rifles can at least use cartridges loaded with cast lead bullets. If you find one chambered in an older cartridge like the .45-70, you can work up very effective loads using black powder, if you have enough primers.
While handguns are easy to carry and keep with you at all times, they should be seen as a last-resort weapon against the undead.
To get good with a handgun requires a lot of practice, something that isn't practical when ammunition is scarce. They should be reserved for desperate, close range encounters. But always remember to keep one last round for yourself--because getting eaten alive sounds pretty awful.
After time, they run into the same ammunition issues as assault rifles. However, handguns can reliably run with loads made with cast lead bullets and black powder like a lever gun, making the possibility of making fairly reliable ammo feasible.
While ammunition is plentiful, a 9mm will be your friend because of a high ammo capacity and low recoil. If you can find the components, a .45 ACP semi-auto is the most forgiving in terms of reloading ammo.
When you come down to casting your own bullets and making your own gunpowder, a revolver chambered in a cartridge with a case large enough to fit a useful blackpowder load is what you're looking for. A .45 Colt wheelgun would be great.
Shotguns are powerful, versatile firearms, and even an 40-year old pump-action shotgun is a formidable defensive tool. It also could be one of the best guns for zombie extermination. Any hunter knows that a long barreled shotgun can be extremely accurate at 50 to 60 yards with a solid pattern of pellets. With the right choke, that can be pushed a bit farther. And if turkey hunters can routinely hit a bird's head at 40 yards, they can certainly do the same with a zombie noggin.
A short barreled shotgun would be advantageous in, say, a hallway, and would provide more of an error of margin when it comes to headshots than a pistol or rifle. You might even be able to get multiple zombies with one shot. And if you aim a little bit low, a 12-gauge load of buckshot might just take the rotted head clean off.
Semi-autos can be finicky about ammo, but pump guns would be very reliable. Though they only offer two shots at a time, there's very little that can go wrong with a break action double barrel.
At the onset of a zombie apocalypse, when there are literal herds of the undead roaming about and ammo is still plentiful, having a few heavy machine guns or LMGs to defend semi-permanent positions could be useful. Even if they don't score multitudinous headshots, they can effectively chop crowds of zombies off their feet and stop an advance.
But, their use would have to be carefully considered, as the ammo they expend in a minute of firing could keep a rifle loaded for a long time.
Something that fires a cartridge that wouldn't be practical in a rifle is preferable here, like a .50 BMG. Might as well use em up while you got 'em.
If you're talking about surviving the onset of a zombie apocalypse, whatever can kill zombies best is the right way to go. An assault rifle of some kind would probably be the most versatile choice. That along with a handgun and some kind of melee weapon would be a solid loadout in the early rounds.
But as time wears on, and ammo becomes harder to source, machine guns and semi-auto pistols and rifles will be the hardest guns to keep running. Lever guns and revolvers will be next, unless folks get real good at casting uniform lead bullets.
By the later rounds, shotgun shells will be the easiest ammunition to reload for the longest period of time if manufacturing and supply lines don't return. They can be filled with a variety of projectiles, have known black powder loads that can be replicated (assuming gunpowder can be produced), and operate at fairly low pressures.
But there's one point of failure for all of these options: primers.
Creating reliable primers in a post apocalypse would be extremely difficult if not impossible, and even attempting to do so is extremely dangerous, because you'd be dealing with volatile explosives--and that's if you could somehow source the necessary components and make a primer, by hand, from scratch or from spent primers. This also goes for percussion cap blackpowder guns.
For the long term, the most viable firearms would, ironically, be flintlock rifles, pistols, and certain "shotguns." In fact, a moderately skilled machinist could probably build a smoothbore flintlock firearm from scrap that would function pretty well.
The only thing necessary to keep such a gun running is gunpowder and flint, which can be sourced from nature. Of course, some kind of projectiles would have to be produced, but a smoothbore can fire little bits of almost anything in a pinch, from marbles to screws. There would be lots of lead laying around, and if a permanent village could be set up and secured, cast lead bullets or musket balls and lead shot can be made fairly easily.
Of course, these are single-shot firearms. So to accompany a flintlock long gun, a pistol and a melee weapon would be necessary. At minimum, a large heavy knife would be required. Some kind of short sword would be OK, but there's something we have to remember. Unlike TV, in real life, driving or hacking through a skull of solid bone with any kind of blade is damn near impossible. You would have to stab a zombie right through the eye socket or under the jaw with a long enough blade to damage the brain.
Instead, a good heavy club that can cause massive head trauma with a single stroke, and won't get stuck in a zombie's skull, is the ideal hand-to-hand weapon in this case. Think the trench clubs improvised by soldiers in WWI or medieval mauls.
Pikes and spears would also be effective against small groups of zombies, especially when used to keep them at a distance or to spear them so they can be more easily dispatch in some other way.
So there you have it. We'd be back to flintlocks and clubs if we survive the zombie hordes long enough.