All of you that watch my reviews on GunsAmerica Digest have probably noticed that I have been shooting left-handed for most of this year. And it wasn’t because I got bored of being a righty. Last year around February, I ended up with a massive blood clot in my right shoulder, which has prevented me from shooting with my dominant hand ever since. And right after I got out of the hospital, we found ourselves in the Planned-demic. Which was obviously a source of stress.
As the COVID 19 madness started to unfold, I found myself in a precarious position. For the first time in my life, I really had to think about recoil sensitivity. Laughable a month prior. I was the guy that spent years shooting hundreds of rounds of 300 Win Mag per week, sponsored by Uncle Sugar. But now I was in a spot where I really needed the softest shooting gun I could possibly find, that still fired a lethal enough bullet to matter. If things went really pear-shaped, was I going to follow the doctor’s orders and shoot lefty in the street battle? Not likely. But I did need to worry about my longevity, as I have children that depend on me.
So I turned back to the barrel length for an AR that God forgot. The red-headed stepchild, the 18 inch. And for reasons we will cover in a minute, the perfect option for anyone worried about recoil. As you probably also remember, guns started flying off of shelves when COVID hit the news. However, parts were still available, at least for a while. Which left me the option of rolling my own.
I opted for an Aero Precision fluted barrel, in the aforementioned length. While recoil was a primary concern, I also took some lung damage from the clots. So my cardio fell apart, literally overnight. A fluted barrel gave me a very good balance of light enough to carry in this state, but heavy enough to mitigate some of the recoil. Anyone that has ever carried a mountain hunting rifle then fired the same caliber in a heavy tactical configuration knows what I am talking about. The fluted barrel also offered a good level of rigidity, cooling, and not heating up as fast as a pencil profile. MSRP $259
The handguard I chose was a bit of an indulgence, so know that there are cheaper handguards as an option. I picked the Geisselle 15 inch Mk4 in Desert Dirt Color, which set me back around $300. That is steep, but it does ship with a low pro gas block, which offsets the cost somewhat. A cheaper handguard would have been fine, but I always wanted one of these. Besides, if it’s the apocalypse, you know I’m going in style. The 15-inch model gives plenty of real estate for a modern grip, as well as provides optimal leverage for a bipod.
With the parts out of the way, why does an 18-inch recoil less than a 16 inch? Or does it even do so at a noticeable level? Yes, and the science here makes sense if you really think about it. Simplifying things just a bit, here is what happens with your AR 15 when the firing pin lights the primer. The bolt is locked closed. The round explodes, contained by the case, and slams the bullet into the barrel. The barrel is basically now plugged, with the hot expanding gasses of the burning powder pushing the bullet down the lands and grooves.
If you look at AR 15 barrels, you will see them listed with 4 different lengths of gas system. Pistol, Carbine, Mid, and Rifle length. And if you laid 4 barrels out side by side, you would notice that the ports are all different distances away from the chamber, rifle being the furthest. Could you, in theory, run a Pistol length gas system on a full length rifle? Maybe. But you wouldn’t want to. This is why.
As our bullet is traveling down the barrel, when is gas pressure the highest? Right when the bullet enters and plugs the barrel. As the bullet goes down the barrel, even with some powder still burning, we essentially get a greater space for our gasses to expand. More open barrel space, a bigger containment cylinder if you think about it. As the bullet passes the gas port, gas is forced into the gas tube, which travels back and cycles our bolt. So the further that gas port is away, the less pressure is coming rearward, and the longer it takes before the gas enters the tube and unlocks the bolt. With less pressure in the gas tube and the few milliseconds longer it takes to reach the gas tube we get less pressure everywhere and slower speeds out of our bolt carrier. Hence less recoil. So ironically enough, our shortest guns have the highest bolt speed, highest felt recoil, and slowest velocities. All other things being equal.
Since the port is at 12 inches on rifle length system, why can’t we just put a rifle length system on a 16-inch barrel? Ahh, good question. Because of another factor called dwell time. Which is some serious nerd stuff, and I wouldn’t even know this if I hadn’t shot for a rifle company years ago. As the pro shooter, you end up doing a lot of testing of new designs. My company was attempting to put a rifle length gas system on a 16.5-inch barrel, and never could get it to work. Because of dwell time issues.
Dwell time is the amount of time that the bullet is still in the barrel after the gas is routed into the gas tube. This is important because the bullet still has to act as a plug in order to keep the pressures high enough to cycle the bolt. The millisecond the bullet exits the barrel, the gas takes the path of least resistance out of the pressure system. So if your timing is off, you will lose pressure prematurely and have a very unreliable gun. It isn’t actually uncommon to see an 18-inch barrel with a mid-length gas system, as 18 is even kind of pushing the limit for a rifle length system.
Combined with a PWS FSC, this system was incredibly soft shooting. So soft shooting in fact, that I had to swap the buffer in my lower from a heavy to a normal to fire anything except 55-grain high-velocity rounds. It feels like a 22LR, which is hard to believe unless you have tried it. For my injured self, it was a match made in heaven.
So while 18-inch barrels are rare, they are available. Daniel Defense makes an excellent one in the pro series models. Barnes Precision Machine makes one, as does Lone Star Armory, and Odin Works. 16 inch is by far the most popular, being the shortest legal on a rifle without a tax stamp. But the benefits to an 18 make it something you should reconsider. For that little bit more length and weight, you get a softer shooter, as well as a minor bullet velocity gain. It is absolutely worth trying out.