Earlier I wrote that carbines did not need to be as accurate as long range rifles. That is because they are intended to be employed in close range situations, where pinpoint accuracy is not supremely necessary. Certainly accuracy is still desirable as hits can not be achieved without some degree of it.
The carbine versions of the AR-15 will usually be fitted with Aimpoint red dot sights or Eotechs or a low powered scope. These optics are geared for speedy shooting at close ranges, rather than pinpoint accuracy at the longer ranges. However, a skilled shooter can accomplish great feats even with red dot sights or 1-4 power scopes.
Accuracy is great, but reliability is what shines when it comes to AR-15’s. Reliability is important in any firearm, but it is especially critical in one used to defend lives. The AR-15 used for defense must work every time, or the consequences could be disastrous. That is why it pays to do the research before purchasing a particular firearm or accessory. Keep things simple, and look for quality before price.
For the defensive role, I would select a carbine model that would offer the extra security of a magnetic particle tested bolt, a chrome lined 1/7 or 1/8 twist barrel of 4150 steel and the proper 5.56 chamber for reliability. With the extra steps taken in the inspection process, the marksman will not have to be concerned about hidden flaws, which could generate a malfunction at the wrong time.
I’d take a hard look at a Colt, LMT (Lewis Machine and Tool) or Noveske built gun. The Noveske AR-15’s offer models with stainless steel barrels, too. In addition, there are several “custom” builders who use excellent parts and put together extremely accurate, reliable rifles. You pick your flavor and pay your cash. If you’ve already picked another brand, just make sure the bolt carrier key screws are properly staked. Also, on adjustable carbine stocks, check for staking on the castle nut. Parts can loosen with use and cause malfunctions, and they could occur at the wrong time.
The flat top configuration with the removable carry handle/rear sight is the most desirable. The flattop design makes the AR-15 more versatile, and if you still want to use the iron sights, just leave the carry handle installed.
The AR-15 trigger is designed to be used under harsh conditions. It’s not going to “feel” like a match trigger, especially in a carbine used for defense. A shooter can expect a 5 to 8 pound trigger release and sometimes heavier, which fits within the military technical parameters for these rifles.
My carbines fall into this “standard” range, and my Colt HBAR Elite utilizes a stainless “enhanced” trigger. The enhanced combination comes with a lightened hammer and teflon coated springs. It breaks at a fairly clean 5 pounds, and it is very satisfactory in performance.
There are several AR-15 triggers available on the market for a variety of uses, and these all have their place in the overall world of shooting the AR-15. Geissele’s offerings are well known and respected trigger/hammer units that come highly recommended by many AR-15 users. There are others from Accuracy Speaks, Chip McCormick, Timney, JP Enterprises, and the list can get quite long. I still maintain that for home defense use, a carbine with a standard trigger is best. The standard trigger is rugged and won’t lose adjustment, because there is none. That makes it reliable and foolproof.
Whether mounting Aimpoints or conventional optics, some of the best solutions for doing so are manufactured by Larue Tactical. The Larue quick release mounts are finely machined and anodized aluminum, and the lever tension is adjustable. The Larue LT-104 SPR-1.5 mount is the one I use on the Colt HBAR Elite. This unit allows the optic to be positioned far enough forward to gain proper eye relief, and this attribute is more important to me than the quick detachable feature. There are lower and higher versions available, and there are also extended models offered. There are other quality mounts for attaching optics on the AR-15, so a shooter has to explore the options and then decide what fits his needs.
On my carbines, Larue quick detachable mounts hold Aimpoint M2’s, and Larue back up sights are fixed in place. At one time the M2’s were the latest and greatest, but Aimpoint has newer models now. I’ve seen no compelling reason to change, however. The advantage of the newer models will be longer battery life and a choice of a smaller 2 m.o.a. red dot. I like the 4 m.o.a. sized dot, because it is fast and easy to see.
Some shooters employ folding sights for a cleaner view through the Aimpoint, but the Larue sight is always ready. I believe a backup sight should be instantly available, and there is nothing more instant than an upright sight aperture fixed in place. Folding sights such as the Troy Industries unit certainly have their place, especially when a magnified optic is used that must be placed over the folded sight to gain the proper eye relief.
Up front, the standard M4 configuration hand guards of my carbines have been replaced with Knight’s Armament M4 RAS (Rail Adapter System) assemblies. Rails allow a light and/or vertical grip for shooter use, and there are many offerings on the market. I chose the KAC because of their reputation for quality, plus I wanted to be able to quickly remove the lower portion of the rail for wiping off the barrel should the need arise. To me the ease of field maintenance outweighs any gains in accuracy a free float assembly might offer for short range use.
Many of the free floating units require barrel or gas block/sight removal for installation. There are other rails available such as the Daniel Defense “Omega” that can be installed or removed without any disassembly. The Larue offerings in free float rails also have a large following, but these require barrel removal for installation.