Inside our Shooters’ Forum, one member recently asked: “What makes an AR accurate? What parts on an AR can actually affect accuracy – for example free-floating handguards, barrels, bolts, bolt carriers?” He wanted an honest, well-informed answer, not only sales pitches. Robert Whitley posted an incredibly comprehensive answer to this inquiry, depending on his experience building and testing lots of AR-15 stripped lower receiver. Robert runs AR-X Enterprises, which produces match-grade uppers for top Power competitors, tactical shooters, and varminters.
There are tons of things which can be done for an AR to enhance consistent accuracy, and that i take advantage of the words “consistent accuracy” because consistency is an element of it (i.e. lots of guns will provide several great 5-shot groups, but won’t do an excellent 10- or 20-shot groups, and a few guns will shoot great one day and not so good on others).
Allow me to share 14 key things we think are important to accuracy.
1. Great Barrel: You’ll desire a premium match-grade barrel, well-machined with a good crown along with a match-type chambering, true to the bore and well cut. The extension threads also needs to be cut true towards the bore, with everything else true and then in proper alignment.
2. Rigid Upper: A rigid, heavy-walled upper receiver aids accuracy. The standard AR upper receiver is made to get a lightweight carry rifle and they also stripped all of the metal they could off it making it light to handle (that is advantageous for the military). The world wide web result are upper receivers which are so thin you are able to flex all of them with your bare hands. These flexible uppers are “strong enough” for general use, but they are not well suited for accuracy. Accuracy improves with a more rigid upper receiver.
3. True Receiver Face: We’ve discovered that truing the receiver face is valuable. Some may argue this aspect but it is always best to keep everything associated with the barrel and also the bore in complete alignment with all the bore (i.e. barrel extension, bolt, upper receiver, carrier, etc.).
4. Barrel Extension: You need to Loctite or glue the barrel extension in the upper receiver. This holds it into position completely front to during the upper receiver. Otherwise if you have any play (and there typically is) it merely hangs around the face in the upper receiver completely determined by the face area of your upper receiver as being the sole way to obtain support for the barrel as opposed to being made more a fundamental element of the top receiver when you are glued-in.
AR-X AR15 Upper5. Gas Block: You need a gas block that fails to impose pointed stress around the barrel. Clamp-on types that grab all the way up throughout the barrel are fantastic. The blocks that are pinned on with tapered pins that wedge from the barrel or maybe the slip on sort of block with set screws that push up from underneath (or directly on the barrel) can deform the bore within the barrel and will wreck the accuracy of any otherwise great barrel.
6. Free-Float Handguard: A rigid, free-float handguard (and I emphasize the phrase rigid) really is important. There are lots of types of free-float handguards and a free-float handguard is, in and of itself, a huge improvement over a non-free-float put in place, but best is a rigid set-up. Some of the ones on the market are small diameter, thin or flexible and when you are shooting off almost any rest, bipod, front bag, etc., a rigid fore-end is best since ARs want to jump, bounce and twist if you let an attempt go, because the carrier starts to begin its cycle before the bullet exits the bore.
7. Barrel Contour: You want some meat about the barrel. Between your upper receiver and the gas block don’t go real thin using a barrel (we love 1? diameter if it’s workable weight-wise). Once you touch off a round as well as the bullet passes the gas port, the gas system immediately starts pressuring track of a gas impulse that provides vibrations and stress on the barrel, especially between the gas block returning to the receiver. A heavier barrel here dampens that. Staying a little heavier with barrel contour with the gas block area and to the muzzle is good for the same reasons. ARs possess a lot happening whenever you touch off a round along with the gas system pressures up and the carrier starts moving (all prior to the bullet exits the bore) hence the more situations are made heavier and rigid to counteract that the better – within reason (I’m not advocating a 12-lb barrel).
8. Gas Tube Routing Clearance: You need a gas tube that runs freely from the barrel nut, with the front of your upper receiver, and thru the gas key within the carrier. Ensure that the gas tube is just not impinged by any kind of them, so it will not load the carrier inside a stressed orientation. You don’t want the gas tube bound up so that if the gas tube pressures up it immediately would like to transmit more force and impulse towards the barrel than would normally occur. We sometimes spend a 63dexjpky of your energy moving the gas block with gas tube off and on new build uppers and tweaking gas tubes to have proper clearance and alignment. Most gas tubes do need a little “tweaking” to have them right – factory tubes may work OK nonetheless they typically will not function optimally without hand-fitting.
9. Gas Port Tuning: You wish to avoid over-porting the gas port. Being over-gassed makes the gas system pressure up earlier and a lot more aggressively. This causes more impulse, and increases forces and vibration affecting the very best end and also the barrel. Tune the gas port to provide the volume of pressure necessary to function properly and adequately but no more.
10. Front/Back Bolt Play: If accuracy is the game, don’t leave lots of front/back bolt play (ensure that is stays .003? but a maximum of .005?). We’ve seen factory rifles run .012? to .015? play, which is OK if you wish to leave room for dirt and grime within a military application. However, that volume of play is just not suitable for a very high-accuracy AR build. A lot of front/back bolt play allows rounds to be hammered in to the chamber and re-formed in the non-consistent way, since they are loaded in to the chamber.
11. Component Quality: Use good parts coming from a reputable source and stay wary of “gun show specials”. All the parts usually are not exactly the same. Some are great, some are not so excellent, and several aftermarket parts are just bad. Don’t forget to work with mil-spec-type carriers; by and large these are excellent for an accuracy build. Also, remember that just because a carrier says “National Match” or something that is else upon it does not necessarily mean it’s any better. Be skeptical of chrome-plated parts since the chrome plating may change the various components dimensionally and will also make it difficult to do hand-fitting for fit and performance.
12. Upper to Lower Fit: An effective upper/lower fit is effective. For fast and dirty fit enhancement, an Accu-Wedge in the rear helps a lot. The ultimate option is to bed the upper to a specific lower so the lower and upper, when together, are more like one integral unit. For your upper receivers we produce, we attempt to have the specs as near when we can, but nevertheless fit the many lowers available in the market place.
13. Muzzle Attachments: Don’t screw up the muzzle (literally). Leave as much metal on the barrel on the muzzle as you can. People love to thread the muzzle for the flash hider, suppressor, muzzle brake, as well as other attachment, however, if you truly want accuracy, leave just as much metal that you can there. And, in case you have a thing that screws on, set it up up to ensure that it may be placed on and also have it stay there without putting a great deal of torque and stress on it right where bullet exits the bore. If you are intending to thread the end of the barrel, ensure it is concentric together with the bore and make certain everything you screw on the website is really as well. For all muzzle attachments, also be sure that the holes whereby the bullet passes through are dead true towards the bore. Many aftermarket screw-on everything is not good this way. Something that vents gas should vent symmetrically (i.e. when it vents left, it ought to vent equally right, and likewise, when it vents up, it will vent down equally). Uneven venting of gas can wreck accuracy.
14. Quality Ammunition: Ammo is really a whole story itself, but loads which are too hot typically shoot poorly in best AR 15 brands. If you want accuracy away from an AR-15, avoid overly hot loads. Shown here are test groups shot with four (4) different uppers, all with moderate loads. These four uppers all basically had the identical features and things completed to them as explained in this article, plus they all shot great.