“Your barrel is going to be how short?” my friend asked as he laughed out loud. My response was, “7.3 inches, about as long as a G36K.”
“A what?” he asked…This was going to be a long conversation.
I’ve been building ARs for a few years now and have always started by choosing a barrel, then designing the weapon on paper before any money gets spent. It keeps my wife somewhat happy that way. The reason for the emphasis on the barrel is because the barrel always dictates what the weapon is slated for. A quality 20-inch barrel means sub-MOA accuracy for the sharpshooter, but very little mobility or practicality for the patrolman. Whereas a 16-inch barrel delivers a somewhat decent balance of the two but is still way too long for comfortable work in a CQB environment. So how does one find the balance between accuracy and mobility? Ah, that is the question, grasshopper.
My first AR was “many moons ago” and, yes, it had a 16-inch barrel. Don’t get me wrong, the 16-inch barrel is a great barrel but one can do better without losing a lot of accuracy. Standard carbines are fine but to make a great patrol carbine you have to go shorter, way shorter.
Short Barrel Rifle (SBR)
I was ready to go on this one and then I started second guessing myself. First, did I really want to spend the $200 on the Class III tax stamp, and second, would it be accurate enough? I had always heard a few schools of thought on the subject like, “SBRs are impractical because their short barrels aren’t very accurate.” Okay, define “accurate.” That’s like trying to define “normal.” We’ve all heard the saying, “Normal is relative,” right? Well, so is accuracy. Accuracy is “relative” to the weapon’s role. Just as normal is relative to how weird those around you really are…Thanksgiving with the family? You have no idea!
Another way to answer this “accuracy” question is like this. Acceptable accuracy is contingent on what you demand of the particular weapon at hand. For example, a 3.5-inch grouping at 100 yards is outstanding accuracy for an SBR with a 7.3-inch barrel. However that same number is a joke when you’re talking about a dedicated sniper rifle that should be able to hit a 50-cent coin in three separate areas at the same 100 yards. The other obstacle is that SBRs are Class III restricted.
SWAT teams have known the virtues of SBRs for years. For “slicing the pie” or engaging through the windshield there is no better carbine than an SBR. Also, try bailing out of your patrol car with a 16-inch carbine; it can get exciting. If you’re rolling to a call that’s gone “Hot,” logic mandates you get that carbine down and sling it around your neck just in case you need to bug out fast upon arrival. Where are you going to tuck that extra foot and a half? That’s right, that barrel has to go somewhere, and it usually ends up between your legs. If you had an SBR, however, it would neatly rest at your side even while seated. With the stock collapsed it’s exactly 24 inches long. Yeah, that’s small, but it’s still a whole lot of stopping power in one place.
The first step in building an SBR is the purchase of a lower receiver. Once you have your lower, you’ll need to get it registered with the ATF. Don’t worry, this is easier than you think. The ATF Form-1 is self-explanatory; follow the instructions on the ATF website and you’ll be cleared in no time. Then comes the fun part, building time. You’ll want to invest in an armorer’s video and specs manual to assist you, or find a pal like me that can help you and laugh at you, I mean with you, when you pinch your fingers. Don’t worry, it’s not rocket science.
For my parts I turned to Tennessee Police Supply because I was tired of using parts that I’d bought off the web with expensive shipping only to find them less than pristine. Tennessee Police Supply is a unique business in that you can usually find them at a large majority of the southeastern gun shows. This is great because it allows you to put your hands on the parts that you’re going to build with before actually buying them. Now, parts really make the weapon; however, sometimes components fall between the cracks, literally. The last few carbines that I’d built hadn’t really “blown my skirt up.” Why? Because I’d received kits from certain AR companies that were missing essential parts, and let’s face it, unlike a VW Bug pretty much every part on any top of AR is essential.
After securing my parts kits I turned to Spike’s Tactical for my lower. Their ST-15 lower caught my eye because it looks like a HK416 because of the color-filled bullet markings. The engraved spider logo also gives the lower a rugged and unique appearance, not to mention second looks on the gun range. Now I know that some of you are asking, “Why build with Spike’s Tactical lowers, wouldn’t it have been better to go with insert your favorite AR company here?”
I know that the words that I’m about to say are “fightin’ words” to some, but they’re for your own good, so here goes. All mil-spec lowers are pretty much the same regardless of their manufacturer. Why am I saying that? Well, I’ll tell you what I tell anyone looking to build their dream AR. If you want resale value, or bragging rights, stick with some of the bigger names out there. Of course, you’ll pay twice the amount for the “Honor;” trust me, been there twice. If you’d rather save money on your lower, so you can order that custom upper (and remain happily married) buy a Spike’s Tactical. Having built with several different brands in the past I was truly impressed with Spike’s lower. The fit and finish is superb and the price ($115 at the time of this writing) just makes it all the sweeter.
The actual assembly of an SBR is pretty much the same as any other AR clone. The only difference, of course, lies in the barrel length. Now I normally start with the lower because it only takes about 30 minutes to build one. I won’t bore you describing the build procedure of the lower, that’s what the video is for. I will say this, pay attention to what you’re doing. There are several ways to lose skin when building a lower so take your time and bring bandaids. There will also be cursing involved in this process so send the kids over to grandma’s for the evening. Remember that the lower assembly is pretty much the actuator and shock absorber of an AR, which means that everything is under spring tension, so remember where those pieces land; you’ll need them.
Before installing any of the lowers parts, you’ll want to decide if you’re intending on sticking with the mil-spec parts that came in your kit or going with plan B. If you’re like most American AR-addicts, good enough is just not good enough. Luckily there are a myriad of products on the market to add functionality and individuality to your AR. Here are some of the few that I chose on this build.
First I replaced the standard A2 mil-spec pistol grip, which is a fine grip but there is always room for improvement, always. Ergo Grip, for example, makes an outstanding pistol grip (4000 series) upgrade that is stiff polymer over-molded with a solvent-resistant, textured rubber for added grip. The ergonomics are truly remarkable and add to your accuracy in notable ways. Also, the grip has a storage compartment with an attached plug, so no more searching if it happens to come loose. The next part to go was the standard triggerguard; it was replaced with a Magpul Enhanced Trigger Guard. It features a shallow “V” shape similar to that of an HK G36K. It’s made of aircraft aluminum, has comfortable rounded edges, and makes shooting with gloves on a lot easier. It also fills the annoying gap at the rear of the standard AR triggerguard, thus eliminating the need for a “gapper,” and yes, it looks very cool.
Next to go was the safety selector for a DPMS ambidextrous selector. It’s double sided and makes life easier on everyone. Since I’m a lefty, I’m big on ambidextrous parts, so for my sling mount I chose to go with a Yankee Hill Machine (YHM) Ambi Sling Loop Adapter installed in place of the mil-spec plate. It allows for multiple sling types and quick transition from lefties to righties. To finish my lower I chose a classic 4-position stock. I prefer it because it’s small and doesn’t snag when you need to bug out of your car quickly. Another part to consider is a rubber stock pad from Pro Mag. It helps your stock grip tightly to your shoulder even over the top of your shield. Yes, I know that your shield goes on the left side of your chest, and that about 80% of those reading this article are right-handed. However, someday you may find yourself having to transition to your opposite shoulder so as to clear a left-handed corner. Think about it.
Next comes the upper assembly build. like the lower it, too, has similar amounts of cursing involved, but is a bit more technical in that not all parts are of the drop-in, or screw-in kind as is the case with a lower. The barrel requires several specialty tools and has to be torqued just so. Also, the gas tube must pass through the barrel lug sprockets cleanly or the bolt won’t cycle properly. Then there are the custom free-floating handguards, which can be a pain to install because the front sight tower has to come off, and mil-spec parts have to be swapped out for custom pieces. I admittedly had never built an AR with a 7.3-inch barrel, so I asked Shawn Temple of Tennessee Police Supply to build my upper for me. Recognizing knowledge greater than your own and accepting it is wisdom indeed.
Shawn built my upper by starting with a high quality, Del-Ton M4 A3 upper with integrated feed ramps. The feed ramps are a big plus when things start getting hot and dirty. The barrel is a 7.3-inch CMMG chrome-lined 5.56mm, with 1-in-7-inch twist. Remember folks, barrels are everything, so spend money on a good one.
The barrel is shrouded in a YHM carbine length quad rail, with free-floating handguard. The quad rail completely covers the full barrel length and a low profile CMMG gas block. All that protrudes from the end of the handguard is a very intimidating YHM 5C2 Flash Suppressor. The suppressor is bladed for a multitude of viable reasons, so use your imagination. Two (non-lawsuit causing, thug upsetting) uses that I have found are as a glass punch and bolt cutter. Some people call the 5C2 a barbed wire cutter; please, that’s what your multi-tool is for. No, this bad boy is meant for bigger and tougher problems. For example, our troops are currently using it to cut locks in half in one quick shot-and-entry motion. The same idea works here in the states. If Mr. Bad Guy hears you rattling away at his security gate with a conventional bolt cutter, it gives him time to get ready. The 5C2 gives you the option of jamming the suppressor against the slide lock or padlock, automatically centering it with the muzzle end, then blasting it clean in half. And, lest I forget, it actually does its intended job (flash suppressing). It effectively erases muzzle signature at night and makes NVG (night vision goggles) use a more pleasant experience. It’s beauty and the beast all in one.
Being a dedicated CQB gun, my SBR needed a tactical light. I didn’t want a huge spot light that costs more than the gun (okay, I actually did but that costs money), yet it still needed to have some chutzpah. I chose a budget-friendly medium, the Streamlight TLR-1. It delivers 80 lumens of white LED light for 2.5 hours and is waterproof. I then finished off the upper with a L-3 EOTech 552. Its design is unique in that it generates a hologram of a 65-MOA CQB ring with a center 1-MOA dot for long shots. It’s also waterproof to 33 feet. It’s so reliable that once it’s installed you could call your SBR a done deal, which is exactly what I did.
These optics work every time even after the HUD display has been damaged. I decided to run some scenarios with the 552 in the off position just to see how accurately I could engage my targets. No, that’s not a typo, I did say off. Since CQB is mostly point-and-shoot anyway it was second nature to “visualize” the large 65-MOA ring that would normally be floating within the reticle. Accuracy proved to be dead-on, even in high speed shooting at 7 yards. Here I thought this was an original idea of mine only to discover that our troops are already doing the same thing. Basically they breach a dark room, center the subject and…Pop-Pop…Pop! Try it, you’ll be surprised how easy it is to do.
Shooting this SBR for the first time was truly an eye opener. I will admit I was apprehensive about shooting something with such a short barrel. However, it fired smoothly and didn’t “whip up” as an SBR supposedly does. As for the actual accuracy stats, I could sit here and tell you about shot groupings at 25 yards and triple taps at 7 yards…yawn! Or, I could just say, let’s go shoot some stuff!
Seeing as how this is a dedicated CQB gun I didn’t bother doing the usual chronograph, muzzle velocity bit. The fact is that this thing is a “Room-Broom.” It’s meant for down and dirty, room-to-room fighting. With the exception of sighting it in at 25 yards (force of habit) I kept all my rapid-fire scenarios inside of 15 feet. For testing purposes and also to shut up the naysayers, I decided to do some penetration tests with the SBR. I shot up some steel targets, cut a couple of locking bolts and generally had very loud and expensive fun. While setting up my targets one of my friends said to me (with a straight face, mind you), “I’ve heard that those short barrels are only good from here to there.” We were standing 8 feet apart. Alrighty then, start running!
I had also been told by a couple of well-meaning friends that my little SBR was worthless against body armor past 25 yards. It easily defeated a Level-III body armor clad watermelon. Remember folks, bad guys wear body armor too. Using some Hornady TAP hollow point I easily melted high-speed holes through the trauma and chest plates. The damage on the watermelon was…well, gross.
The SBR proved to be very accurate at roughly 21 feet with the L-3 EOTech turned off. It worked well with the TAP and M855, but it did not like the frangible ammo at all. It had extraction issues with it because of its low pressure and bullet weight. Unfortunately, that’s par for the course when dealing with such a short barrel. Along with the SBR’s accuracy came another interesting surprise, a massive pressure wave that pounded my body during firing. I also tried some headshots at distance and was pleased at how easily the SBR could hit at relatively long distances. The 552’s 1-MOA central dot really helped with this and made it feel effortless.
Now I would be remiss if I did not mention this weapon’s one real drawback. It gets dirty in a big way. Because its barrel is so short the SBR doesn’t have enough time to build up proper pressure and heat so as to burn off all the powder in the casing. What you end up with is a thick copper-colored, baked-on mess that sticks to your bolt and carrier. It takes some elbow grease and creativity to get it thoroughly clean. The good news is that even with all that fouling going into your weapon you really have to do a lot of shooting for this weapon to fail.
As I was scrubbing this weapon after some trigger time I felt compelled to add some information regarding SBRs. Terminal ballistics is a big point of contention when you’re talking about energy on target in regards to 5.56mm versus 6.8mm. While it’s true that 6.8mm has greater stopping power than a 5.56mm, it’s worth noting that the 5.56mm round in the heavier loads is currently yielding very effective wound cavities as reported by our spec-ops teams. It is equally important to note that when you are fighting to get ARs into the hands of cops, you take the 5.56mm and thank your lucky stars that your chief had the guts to push for it against city council. But, more importantly, you don’t pull a boneheaded move and say something like, “But mayor, we really feel that the 6.8mm would be better!” Can you say, “delayed due to another research committee?” The fact is that you take the 5.56mm platform and learn to work with it and find ways to maximize its potentials and downplay its weaknesses and, yes, there are several with this weapon.
The greatest weakness is the bullet itself. What’s the solution? Go heavier. This is generally a good choice with any AR but it’s essential to an SBR. You should try and stick with bullet weights that are in excess of 62 grains. Rounds that are in the 75-grain range would be better. The reason for this is that the heavier the load, the more time the round has to cook off, subsequently that translates into more gas and, yes, “having gas” is good in this case. Also the heavier loads will tend to be more effective against the ultimate predator that would be “Mr. Meth-Head” on a rampage. The idea here is to create a combination of bullet and barrel where the round has enough stability to travel to the target accurately, but also one that is unstable enough to yaw and spall on contact with the bad guy. These SBRs are tricky little creations but they are useful.
All said and done, I am truly pleased with this SBR’s performance. Many thanks go to Tennessee Police Supply for providing me with quality parts to build and for the outstanding assembly job on the upper. Thanks also to Spike’s Tactical for their quality lower; they deserve an objective look when you’re considering your patrol carbine or home defense gun. Keep in mind that when you choose your carbine, eventually you should consider a sound suppressor. It saves your hearing and that of the public who is so fond of lawsuits. However, if you begin with a 16-inch barrel and add a 6-inch suppressor, you’re really going to be swinging around a lot of weight. With an SBR you’ll still be well under 16 inches and have manageable lateral sway.
Building your own AR is truly a great hobby. It also saves you money and gives you peace of mind knowing that it’s been done right. By building you can turn those savings into upgrades on your gun.
“Your barrel is going to be how short?” my friend asked as he laughed out…
by Eduardo Abril de Fontcuberta / Oct 25, 2008