Whether it’s a new AR-15 out for the first test drive or one that’s been “resting” in the safe for a while, these fine rifles can experience the occasional hiccup at the range.
Here are a few pointers to quickly determine if the rifle needs some professional attention or just a little maintenance to run reliably.
Lube It Right
Reciprocating parts move better when they’re wet.
The bolt and bolt carrier group in an AR-15 need some oil to move freely and cycle reliably.
Most malfunctions I’ve seen at the range occur because a rifle didn’t have enough lubrication to function.
However, I’ve also seen spray bottles full of lube at the range where some well-intentioned “gun guy” sprayed lube through the ejection port into the upper receiver of a troubled AR-15.
That’s way too much lube in the wrong place and all it really accomplishes is making a mess.
Pull the bolt carrier group out of the back of the receiver and, holding the bolt carrier with the bolt upright, put three to four drops of oil on the bolt body and let it run down inside the carrier.
Two drops of oil on the cam pin is a good idea.
Finally, put two to three drops of oil on the bolt carrier’s flat rails on the top and bottom of the carrier. That’s all it takes to lube an AR-15 adequately.
Checking Your AR-15’s Gas
The AR-15 works by sending gas from the fired cartridge through a small hole in the top of the barrel a few inches from the muzzle.
The gas moves down a tube and into the receiver where it cycles the action.
Too much or too little gas creates problems, but checking to find out what’s happening is an easy task.
An AR-15 that either receives too much or too little gas will exhibit the same problem of leaving a fired piece of brass in the receiver when it tries to load a new round.
The best way to determine if the rifle receives too little gas is to load one round in a magazine, load, and fire.
Repeat this process a few times to make sure the result is always the same.
If a rifle has the problem described above and the bolt locks back on the empty magazine, the rifle has too much gas to work properly.
If the bolt doesn’t lock back, there isn’t enough gas to make the gun run.
Being under-gassed is not an uncommon problem when shooting steel-cased ammunition or PMC ammunition in cold weather.
Understand Your Ammo
Those two types of ammunition are loaded to lower velocity, which makes them great for a day at the range, but the lower velocity can be problematic on a cold day.
Gunpowder doesn’t burn as efficiently in cold weather, so the light loads can cause trouble.
Over-gassed guns usually occur when shooting M855 or SS109 out of an 11.5-inch barrel or shorter with a suppressor. Some solutions for under- or over-gassed rifles are not complex.
Run the Right Buffer
Remove the buffer from the rifle and look on the face to see its type. A buffer weight commonly used is the H-2.
If a rifle is under-gassed, put a carbine-weight buffer in it. If a rifle is over-gassed, get the heaviest aftermarket buffer you can find.
If these solutions don’t fix the problem (after making sure the fault isn’t the magazine), it’s time for a gunsmith.
Putting a little bit of oil in the right places and verifying the rifle is gassed correctly are simple tasks that take just moments to complete.
The solutions outlined above will cure about 90-percent of AR-15 malfunctions.