Though I live in a rural area and my nephew lives forty miles further back in the sticks in an even more rural area, he has been expressing concern about break-ins and the need for a home-defense weapon. The number of home-invasion robberies seems to be on the increase. For the moment, he has settled on his .270 caliber Remington 700. He is still looking. One of his primary considerations is price, and that has to be the case for most of us.
If price is not a concern and a person is looking for one "perfect" weapon, a good choice might be a semi-automatic rifle such as a Springfield M1A, a Heckler & Koch, a Kel Tec RFB (7.62mm/.308) or one of the now-ubiquitous AR clones. Everybody is making AR-like rifles these days from Smith & Wesson to Ruger.
The advantages of the AR's are numerous. The decreased overall length combined with the pistol grip and sight set-up make these little rifles very controllable in close quarters. With picatinny rails, all sorts of lights and lasers and optical sights can be attached. Adding a flash-suppressor to the barrel — if it doesn't come with one — saves night vision. They are lightweight, accurate at longer ranges, capable of high rates of fire, and equipped with high-capacity magazines. In addition these rifles can be fired with reasonable accuracy by almost anyone. The first time I picked one up, I qualified with it at a 100-yard range. My groups looked more like patterns but were good enough for government work.
Our military is still mostly using the 5.56mm which is an excellent choice on ground squirrels. It also appears to work pretty well on bad guys at shorter ranges, and if a weapon is for "home defense", shorter ranges are what we are interested in. For most of us, any rifle is easier to shoot accurately than any handgun. The sight radius is part of it, but the anchor point on the shoulder and the contact point with the shooter's face are even more important for accuracy — in my opinion. The enhanced accuracy potential of a rifle combined with a low-recoiling round like the .223 makes sense for the person whose range time is limited. Ammunition is plentiful and still relatively inexpensive. If it comes to the point of being forced to leave one's home, the AR-like rifles make sense as bug-out weapons. Again the weight, including the weight of .223 ammunition, works in their favor. They are easy to carry and with the right sling can be ready for nearly instant deployment.
Recoil isn't an issue with the .223 in any rifle but especially in a semi-auto where energy is used to cycle the action. This helps soften recoil even if a heavier caliber is used — not much in some cases but some. Lower recoil means less flinching and better accuracy as well as faster recovery for follow-up shots.
So with all the advantages of these rifles, why don't I have one? I've almost talked myself into heading to the gunshop. In fact, however, I have my home defense needs covered. I have always liked my shotgun even with a 30-inch barrel and screw-in chokes. I still like that barrel and my choke choices, but it is less than ideal for using inside the confines of a house. Adding the shorter barrel with rifle sights and a modified choke, as noted here, has turned my 870 into an excellent defensive weapon. Then I also have a number of handguns including my XDM .40 S&W, not to mention my own home defense rifle of a rather different sort. I am not leaving my home under any circumstances so packing ammunition and heavier weapons is not a concern.
Back to the point, what if a person does not want shell out the money for a high-end military-style rifle just to repel boarders? There are other military semi-auto rifles available such as the AK's in various flavors. They may not be as accurate as the AR class, but AK-47's are utterly reliable and pack a little more punch than the .223. Then there are surplus bolt-action military rifles like the Mosin-Nagant, Enfields, and Mausers that combine toughness, reliability, and power. Recoil becomes an issue with the Mosin, as does muzzle blast. Enfields also kick noticeably, and the same is true of Mausers depending on the chambering. It can take a little getting used to.
My solution to the home defense rifle question is, as I said, a little different. I use a lever-action .30-30 Winchester Model 94 Trapper. This little rifle has a 16.5 barrel. With a large aperture receiver sight, a red dot sight, or a low-power scope, the Trapper is very fast on target. The tubular magazine holds only five rounds, but I can shove fresh rounds in the side without swapping out magazines. If I were buying today, instead of the Winchester, I would buy a stainless steel Marlin lever-action. The ancient .30-30 is still a good deer rifle. Ammunition is reasonable and available everywhere. Generally folks disparage the accuracy of lever-actions. My experience has been that this is more an issue of sights than the weapon itself. Most of us will not get the full potential out of a rifle with open sights. A minority of shooters are gifted with exceptional vision. For the rest of us, a good scope will sometimes do more for our groups than a good barrel. When testing out handloads, I slap a scope on the Trapper, and I have fired some very small groups using Speer 130-grain flat-nose over Hodgdon H322 or H4895. Switching back to the receiver sight, which is a better choice up close, and testing the same loads exposes a slight decrease in 100-yard accuracy — all on the shooter.
It is kind of a shame that Ruger no longer offers their semi-auto Deerslayer .44 magnum. That would be a good choice for a home defense rifle. A lever-action in a pistol caliber such as the .44 magnum, .45, or .357 is also a kinder, gentler sort of "assault" rifle. I believe Kel Tec makes some semi-auto .223 caliber carbines which fall into the low end of the AR-class price range in addition to the rather high-end RFB ($1800+ MSRP) already mentioned. Kel Tec also offers its SUB-2000 carbine in 9mm and .40 S&W at a MSRP in the $400+ range — which is not bad.
A home defense rifle is a good idea, though not something everybody necessarily has to have. It should be reliable, controllable, and easily handled in close quarters, but most of all, it should be a weapon with which the user is comfortable and that inspires confidence. Confidence and resolve will often dissuade attackers.