A short discourse on semi-auto Homeland Defense Rifles (HDR). Some term these MBRs, for "Main Battle Rifle." But I'm not in the Army and don't plan on getting in any battles at all; and certainly not so many that I need my main rifle to be a battle rifle! My rifle will be fed reloaded ammo, hunting ammo in most cases, and will be used for target practice, hunting and varmint control, as well as filling the role that Swiss people understand but most Americans have forgotten (which is exactly why we're more likely to need it).
Let's get a few things straight, right up front. This is is where I make some people mad, because I'm just gonna go ahead and step outside convention and tell it like I see it, rather than toeing the party line and wasting my time and yours. So if you can't take the truth, go somewhere else and read the consensus view (which I could quote off the top of my head, but again, there's that time-wasting thing).
First, caliber. The choices are intermediate power vs. full power rifle cartridges. If you place a high value on the ability to stop large bears, disable vehicles, shoot through trees, etc., then you need a full power rifle cartridge. The intermediates will do all of the above, but it may take a few more shots on target to finish the job.
Likewise, if you feel the local criminal gang is gonna show up at your place wearing body armor, the full-power jobs will get it done with perhaps fewer rounds fired; but the intermediates will still get it done. This means .223/5.56, and it also means 7.62x39. Anyone who tries to tell you the 7.62x39 is a full power rifle cartridge is an idiot, a liar, or both. Full power military rifle cartridges include .308 (aka 7.62x51 NATO), .30/06, 7.62x54R, .303 British, all the Mauser military cartridges (6.5x55, 7x57, 8x57 etc.), 7.5x55 Swiss, and many others.
Second, country of origin: who cares! We're looking at design and availability (of the rifles, parts and ammo) here.
If you wish to be pragmatic about it, give up any infatuation with American designs. Only two American military cartridge-firing rifle designs have ever really made the cut. Those two are the single-shot Remington Rolling Block and the AR-15, both of which have been used as a front-line military issue rifle by a substantial number of countries.
But what about the 1903 and 03A3 Springfield? What about the M1 Garand? What about that holy grail, the M14? What about the AR-10?
I'll tackle those one at a time, briefly. I love the 1903 Springfield. I have one. Its quality is wonderful. It is a great deer rifle, and a great rifle with which to while away the hours at the range while not spending too much money, shooting cast-bullet handloads. But as a military rifle, it took the perfect bolt action military rifle (the Mauser 98) and added a few dubious "features" (magazine cutoff, two-piece striker, and a modification of the ejector to allow it to jump the cartridge rim: which it will also do in the other direction, under adverse conditions), all of which served only to make it LESS reliable and more complicated. Even so, I would call it a design that "made the cut," except that it isn't really an American design.
The Garand? It is fairly reliable and accurate, but feeds only with an en-bloc clip that doesn't allow you to top off the magazine, and announces for all the world to hear when it is empty. Without the clips the Garand is a single-shot, and a heavy and bulky one at that. In my opinion it would be a great rifle if only it had a stripper clip-fed box magazine.
The M14? The only military that has adopted it is the US, and that only on a very limited basis (to be fair, Italy did issue the similar BM59 for awhile). It is considered a premium item, and costs two to three times what a basic G3 or FAL costs. Also, I have always heard of reliability issues in adverse conditions, and of safety issues when they get much wear on them (which they usually don't, because nobody uses them for front-line duty). Note that I am only reporting what I have heard here, and have no personal experience with the design. I probably would have experience with it if prices didn't start at about $1600; or if George H.W. Bush hadn't decreed that we shouldn't be allowed to buy sub-$500 Norinco M14s.
The AR-10? Well, it has the disadvantages of the AR-15, while lacking enough of its advantages to make it, in my opinion, a good choice. It is becoming slightly more of a commodity item because of its similarity to the AR-15, but no major military uses it as a main battle rifle.
The real reason the US has always kicked butt in the wars is because we are riflemen. Yes, even now to a large degree. Most of the guys who actually use rifles in the US military, love rifles and love getting paid to train fulltime at things they would likely do for fun otherwise, in the form of action shooting competition, long-range target shooting, paintball, etc, etc.
US soldiers in WWII turned the disadvantage of the Garand's announcement of its empty condition into an advantage, by flipping an empty clip into the air to simulate an empty rifle while holding the loaded rifle at the ready.
And because we love our rifles, we have no problem with the fact that American military rifles have always been maintenance-intensive. We just go ahead and pull the required maintenance.
American troops could be issued Carcanos and would still kick butt; undoubtedly while proclaiming how wonderful and superior the Carcano rifle is!
So, back to the main topic. What are some good Homeland Defense Rifle choices? Let's deal with the intermediate cartridges first. The "big three" here are the AR-15, the AK-47 pattern, and the SKS. Anything else is just too hard to get parts for. The AK is very reliable and parts and magazines are very readily available. They are not well known for accuracy, though. Actually they are well known for their lack thereof. Also, the safety, while positive, is not very ergonomic and is noisy in operation.
The SKS is a wonderful Homeland Defense Rifle. It used to be considered an extreme budget alternative to the semiauto AK. Now that it costs as much as a semi AK however, it is proving to STILL be popular. Why? Because it is a very good rifle. Good power level (same as the AK), more accurate than an AK, ergonomic and easy to shoot. It handles cast bullets very well for long hours of cheap target practice, not to mention hunting deer and smaller game. The 10-round, non-detachable magazine with a quick release catch for easy unloading, and topside loading via stripper clip or loose rounds, works very well for both utilitarian and defensive purposes. Overall, a very good homestead/defensive rifle.
The AR-15 has become also a good choice; the number-one choice for most, in fact. They are used by many military forces worldwide, and parts and complete rifles are produced by many, many companies. They have been much-modified, and have become even more of a commodity rifle than the Mauser 98. Also, you can have one lower receiver (the serial numbered and hence regulated part) and multiple complete uppers set up for various purposes. Perhaps a carbine upper for defense, a heavy-barrel, free-floated, scoped, 6.5 Grendel upper for long range targets (and fulfilling the role of an expensive .308 HDR), and perhaps a .50 Beowulf (or .458 SOCOM, or .450 Bushmaster) upper for dealing with those pesky grizzlies in the garden, and a pistol-caliber upper for cheap plinking, indoor range use etc., and of course a .22 LR upper or conversion kit for ultra-cheap plinking and small game hunting.
In my opinion, the best overall way to go would be an intermediate caliber semi-auto military rifle (SKS, AR-15 or AK) and a good military bolt action full power rifle complete with plenty of ammo and stripper clips. A Mauser 98 in 8x57, .30/06 or .308 would be my first choice. My second choice would be a Springfield or a P17 Enfield. Both are expensive, but good choices overall. The extreme budget alternative is, of course, the Mosin-Nagant in 7.62x54R. Some people prefer Enfields. If you have an SMLE, #4 or P14 and are happy with it, I see no reason to disparage that choice, either. Any of the above choices will do the job if you put in the time and effort to become proficient with it.
If you are bent on going the .308 semi-auto route, the two primary choices are a G3 type rifle, or an FAL/L1A1 type rifle. Both are very reliable, popular rifles which have been (and are) used by a great many military forces worldwide. Both have 20 round or larger magazines readily available at cheap prices (usually under $10, which is even cheaper than AR magazines!) and both may even be built from demilled parts kits coupled with an aftermarket receiver, if desired.
Of the two, the G3/CETME rifles are somewhat more reliable under extreme conditions; this is offset by the fact that its delayed-roller blowback (as opposed to gas operated) action and fluted chamber are hard on brass to the point that two or three loadings are probably the maximum you will get from each cartridge case. So if you are an avid reloader, you might be better off with the FAL.
Either of the two would be a good choice. I used to say they were the only really good choices, but the increased availability of AR-10 parts is making me rethink my stance on the subject.
Here are some links to more information.
PTR-91 manufacturer link
Gunblast CETME article
G3 on Gunpedia
Wikipedia on the FAL