I field a ton of questions from people who don’t what they want in an AR-15 or that think they know what they want but don’t know why. I’ve got one buddy who has asked me so many AR questions in the last month that I’m thinking about changing my phone number.
My opinions on AR are just that—opinions. If you disagree, please register and comment, I’d love to have some differing viewpoints. The most important aspect to an AR is the barrel, so I’ll address barrel specs first.
If you are not going with an SBR (you have to NFA register anything shorter than 16”) than this is mostly a question of personal taste. I will note that if you go with a 16” barrel, get a full 16” barrel, not a 14.5” barrel with a permanently attached flash hider. The reason for this is that if you ever get a suppressor you’ll need to either take the flash hider off and register the gun as an SBR or you’ll have to get a quick detach suppressor and have a gunsmith permanently attach the corresponding flash hider.
To a certain extent, the longer the barrel is the more velocity the round will have. The velocity really starts to drop off when the barrel gets shorter than 12.5”. Barrel length is going to depend on use. I don’t really have a preference on lengths other than I try to use the shortest one I can to get the desired velocity.
I always want the lightest one available. I think people tend to use WAY heavier barrels than necessary. I don’t mind bull barrels on Varmint/Precision rifles, but when I see guys with heavy barreled 16” guns, it just doesn’t seem right. You won’t catch me with a heavy barrel on a gun unless it is a belt fed. Hell, I wouldn’t even put an M4 or government profile on one of my guns intentionally unless it was select fire. Handling the heat of full auto fire is the only reason to lug all that extra barrel mass around. I prefer pencil or lightweight profiles.
Although tighter twists do slow down the projectile velocity (a round shot out of a 1:7 barrel will have less velocity than one out of a 1:9 barrel), I like heavy bullets, so I tend to go tighter, but anything in the 1:7-1:9 range is pretty normal.
Barrel Materials and Construction
I’m not a metallurgist but I think that the vast majority of people who spout online about different properties of varying grades of steel a) aren’t qualified to know what they are talking about and b) don’t shoot often enough to wear out a barrel or well enough to determine if there is an accuracy difference between barrel materials (probably because they spend more time online arguing about barrels than out at the range). Chrome lined or not chrome lined, sigh, yet another bone of contention. Without getting too far into this I will say I have a strong preference for cold hammered forged barrels in my carbines. Other than that, as long as it shoots well I’m happy.
Gas System Type and Length
Piston systems seem all the rage, but unless you are using a suppressor often or running a SBR, I think there are better places to spend your money. Direct impingement systems work fine. Don’t drink the koolaid.
For gas system length, the longer the better as long as you have enough length after the port so that there is sufficient dwell time. Less than 12” barrel needs a pistol length gas system. On a 12”-16” barrel, it’s a carbine length. On a 16” barrel I prefer a mid-length gas system. On an 18”+ barrel, a rifle length gas system. My reasons for wanting the longer gas system are to smooth out the recoil impulse and (if you are using iron sights) a longer sight radius.
I’m not sure how much I care about the rest of the specs on the gun. I like a lightweight gun without a lot of crap hanging on it. A polymer lower can be a great start if it is from a quality manufacturer like New Frontier Armory. It is almost half a pound lighter than a conventional aluminum lower. These days I’m liking fully ambi lowers—LWRC and American Defense Manufacturing are my favorites with POF right behind.
A great trigger is a must. I’m a Hyperfire fan. Their triggers can have super light pulls and short resets without compromising hammer power or going off if dropped. Truly a unique design in the market.
BCG doesn’t really matter that much as long as the headspacing is correct and the gas key is properly staked.
Furniture is a personal choice. Again, lighter equals better for me.