December 27, 2022 One Shooters Forum member asked: “What makes an AR accurate?” What parts of an AR can affect accuracy? He was looking for an honest, well-informed and not just sales pitches. Based on his extensive experience in building and testing scores of AR-platform rifles, Robert Whitley provided a detailed answer. Robert Whitley runs AR-X Enterprises which produces match-grade AR uppers for High Power competitors, tactical shooters and varminters.
There are many things you can do to improve consistency in accuracy with an AR. I use the term “consistent accuracy” because consistency (i.e. There are many things that can be done to an AR to improve consistency accuracy. A great barrel is a premium match-grade barrel. It should have a well-machined crown and match-type chambering. You must also ensure that the extension threads are cut accurately to the bore. Rigid Upper: An upper receiver with a rigid, heavy-walled body aids accuracy. The typical AR upper receiver was designed for a lightweight carry rifle. They stripped all metal off it to make it lighter to carry (which is a benefit for the military). Upper receivers are now so thin that you can bend them with your naked hands. These flexible uppers can be used for general purposes, but they are not ideal to improve accuracy. A rigider upper receiver improves accuracy. True receiver face: We have found that truer receiver faces are more valuable than we thought. While some may disagree with this assertion, it is best to keep the barrel and bore in perfect alignment (i.e. barrel extension, bolt, upper receiver, carrier, etc.).4. Barrel Extension: The barrel extension should be glued or lubricated into the upper receiver. This will hold it in place from the front to the back of the upper receiver. If there is any play, which is often, it hangs on the upper receiver’s face completely dependent on the upper receiver’s face as the only source of support for barrel. Gas Block: A gas block should not put too much stress on the barrel. The clamp-on blocks that grip all the way around the barrel work well. 6. Free-Float Handguard: This is a rigid, free-floating handguard (and I emphasize that word rigid) that really makes a big difference. There are many free-float handguards. A free-float guard is an improvement over a nonfree-float setup. However, it is better to have a rigid set-up. Some are too small, too thin, and/or flexible. If you shoot off any type of rest or bipod, a rigid fore end is the best. ARs love to jump, bounce, and twist when they are released. This is because the carrier begins its cycle before the bullet exits. Barrel Contour – You want some meat on your barrel. A barrel should not be too thin between the gas block and the upper receiver. We prefer 1? If it’s possible weight-wise, the diameter should be at least 1 inch. The gas system instantly starts pressingurising the bullet as soon as it touches the gas port. This creates vibrations and stress in the barrel, especially between gas block and receiver. This is lowered by a heavier barrel. It is a good idea to keep the barrel contour through the gas block and out to the muzzle a little heavier. 8. Clearance on Gas Tube Routing: A gas tube should run freely through the barrel nuts, through the upper receiver and through the carrier’s gas key. You must ensure that the gas tube does not get in the way of any of these items so that it doesn’t load the carrier in an unsafe orientation. The gas tube should not be clogged so that it transmits more force and impulse to a barrel when it pressures up than normal. Sometimes we spend a lot of our time moving the gas tube and gas block on and off new build uppers, and adjusting gas tubes to ensure proper alignment and clearance. Most gas tubes require some “tweaking” in order to work properly. While factory tubes may work well, they are not designed to be used optimally. Gas Port Tuning: It is important to not over-port the gas port. Over-gassing causes the gas system pressure to rise earlier and more aggressively. This can cause more impulse and vibration, which can affect the barrel and top end. Adjust the gas port to provide the pressure required to function properly and efficiently, but not more. Front/Back Bolt Play – If accuracy is your goal, keep it at.003 But not more than.005?. We’ve seen factory rifles that run at.012? Factory rifles can run from.012 to.015 play, which is fine if you have to allow for dirt and grime in a military app. This amount of play is not ideal if you are building an AR with high accuracy. There is a lot of play between the front and back bolts, which allows rounds to be hammered into a chamber and then re-formed in a non-consistent manner as they are loaded into it. Quality of the component: Only use quality parts from a trusted source. Be wary about “gun show specials”. Every part is different. Some parts are good, others not so good, while some aftermarket parts can be very bad. You don’t have to be afraid to use mil-spec carriers. They are generally excellent for accuracy builds. Remember that just because a carrier has “National Match” or another label, it doesn’t necessarily mean it is better. Chrome-plated parts should be avoided as they can alter the dimensionality of the parts and make it difficult to hand-fit the parts for fit and function. Good upper-to-lower fit: It is important to have a good upper/lower balance. An Accu-Wedge in your rear can be used to improve fit. The ultimate solution is to attach the upper to a lower so that they are more like one unit. We try to match the specifications of the upper receivers that we produce with the lowers available. Muzzle Attachments – Don’t mess with the muzzle. You should leave as much metal as possible on the muzzle barrel. Some people like to thread the muzzle to attach a flash hider or suppressor, muzzle brake, and other attachments. But if accuracy is important, you should leave as much metal there as possible. If you have a screw-on attachment, make sure it can be attached and that it stays put without putting too much torque or stress right where the bullet exits. Make sure the barrel’s end is concentric with the bore. Make sure that all muzzle attachments are centered in the bore. This is a common problem with many aftermarket screw-on items. Any gas venting device should vent symmetrically (i.e. If it vents to the left, it should vent equally to the right. And likewise, if venting up, it should vent down equally. Inaccuracy can be caused by uneven gas venting.14 Quality ammunition: Ammo can be a whole different story. However, loads that are too hot often shoot poorly in an AR-15. Avoid hot loads if you want accuracy from your AR-15. Below are four (4) test groups that were shot with four (4) different uppers with moderate loads. These four uppers had basically the same features and things as described in this article. They all shot great. Robert Whitley
www.6mmAR.com
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