In your Shooters’ Forum, one member recently asked: “What makes an AR accurate? What parts on an AR can definitely affect accuracy – such as free-floating handguards, barrels, bolts, bolt carriers?” He wanted a sincere, well-informed answer, not just sales pitches. Robert Whitley posted an incredibly comprehensive response to this question, based upon his experience building and testing dozens of AR15 collapsible stock. 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 with an AR to improve consistent accuracy, and i also take advantage of the words “consistent accuracy” because consistency is a part of it (i.e. a lot of guns will offer a couple great 5-shot groups, but won’t do a really good 10- or 20-shot groups, and some guns will shoot great 1 day and not so excellent on others).
Here are 14 key things we think are very important to accuracy.
1. Great Barrel: You’ll need a premium match-grade barrel, well-machined with a good crown as well as a match-type chambering, true on the bore and well cut. The extension threads must also be cut true towards the bore, with everything else true and also in proper alignment.
2. Rigid Upper: A rigid, heavy-walled upper receiver aids accuracy. The common AR upper receiver was made to get a lightweight carry rifle and they stripped every one of the metal they could off it making it light to transport (that is advantageous for the military). The web result are upper receivers which can be so thin it is possible to flex all of them with your bare hands. These flexible uppers are “strong enough” for general use, however are not perfect for accuracy. Accuracy improves having a more rigid upper receiver.
3. True Receiver Face: We’ve found that truing the receiver face is valuable. Some may argue this time but it is always best to keep everything linked to the barrel along with the bore in complete alignment with all the bore (i.e. barrel extension, bolt, upper receiver, carrier, etc.).
4. Barrel Extension: You ought to Loctite or glue the barrel extension in to the upper receiver. This holds it set up entirely front to in the upper receiver. Otherwise when there is any play (and then there typically is) it merely hangs in the face of the upper receiver completely reliant on the facial area from the upper receiver since the sole method to obtain support for that barrel rather than being made more an integral part of the upper receiver by being glued-in.
AR-X AR15 Upper5. Gas Block: You desire a gas block that is not going to impose pointed stress in the barrel. Clamp-on types that grab all the way up around the barrel are perfect. 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 inside of the barrel and may wreck the precision of an otherwise great barrel.
6. Free-Float Handguard: A rigid, free-float handguard (and I emphasize the phrase rigid) really is important. There are numerous varieties of free-float handguards along with a free-float handguard is, in and of itself, a huge improvement across a non-free-float set up, but best can be a rigid set-up. A number of the ones available on the market are small diameter, thin and/or flexible and should you be shooting off almost any rest, bipod, front bag, etc., a rigid fore-end is best since ARs wish to jump, bounce and twist if you let a shot go, because the carrier actually starts to begin its cycle prior to the bullet exits the bore.
7. Barrel Contour: You need some meat about the barrel. Between the upper receiver and the gas block don’t go real thin with a barrel (we love to 1? diameter if it’s workable weight-wise). When you touch off a round and the bullet passes the gas port, the gas system immediately starts pressuring track of a gas impulse which offers vibrations and stress about the barrel, especially involving the gas block returning to the receiver. A heavier barrel here dampens that. Staying a bit heavier with barrel contour from the gas block area and to the muzzle is perfect for the identical reasons. ARs have a lot occurring if you touch off a round and the gas system pressures up and also the carrier starts moving (all just before the bullet exits the bore) therefore the more the situation is made heavier and rigid to counteract that this better – within reason (I’m not advocating a 12-lb barrel).
8. Gas Tube Routing Clearance: You will want gas tube that runs freely through the barrel nut, from the front of your upper receiver, and through the gas key within the carrier. Ensure the gas tube is not impinged by any one of them, to ensure that it will not load the carrier within a stressed orientation. You don’t want the gas tube bound up in order that as soon as the gas tube pressures up it immediately would like to transmit more force and impulse on the barrel than would normally occur. We sometimes spend a 63dexjpky of time 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 acquire them right – factory tubes may work OK however they typically tend not to function optimally without hand-fitting.
9. Gas Port Tuning: You need to avoid over-porting the gas port. Being over-gassed makes the gas system pressure up earlier plus more aggressively. This causes more impulse, and increases forces and vibration affecting the top end and the barrel. Tune the gas port to give the volume of pressure necessary to function properly and adequately but no longer.
10. Front/Back Bolt Play: If accuracy is the game, don’t leave plenty of front/back bolt play (make it .003? but not more than .005?). We’ve seen factory rifles run .012? to .015? play, which can be OK if you have to leave room for dirt and grime inside a military application. However, that amount of play is not really well suited for an increased-accuracy AR build. A great deal of front/back bolt play allows rounds being hammered into the chamber and re-formed inside a non-consistent way, because they are loaded to the chamber.
11. Component Quality: Use good parts coming from a reputable source and be wary of “gun show specials”. All the parts will not be exactly the same. Some are perfect, some are not so great, and a few aftermarket parts are simply just bad. Don’t forget to work with mil-spec-type carriers; by and large these are excellent for an accuracy build. Also, do not forget that simply because a carrier says “National Match” or anything else on it does not necessarily mean it’s any better. Be suspicious of chrome-plated parts as being the chrome plating can change the various components dimensionally and will also make it difficult to do hand-fitting for fit and function.
12. Upper to decrease Fit: A good upper/lower fit is useful. For fast and dirty fit enhancement, an Accu-Wedge within the rear helps a great deal. The greatest option would be to bed top of the to some specific lower so that the upper and lower, when together, tend to be more like one integral unit. To the upper receivers we produce, we attempt to find the specs as close since we can, but still fit the many lowers available in the market place.
13. Muzzle Attachments: Don’t screw in the muzzle (literally). Leave the maximum amount of metal in the barrel on the muzzle that you can. People like to thread the muzzle for the flash hider, suppressor, muzzle brake, or some other attachment, but if you want accuracy, leave just as much metal since you can there. And, if you have a thing that screws on, set it up to ensure that it may be put on and possess it stay there without putting lots of torque and stress upon it right where bullet exits the bore. If you are intending to thread the conclusion in the barrel, ensure it is concentric using the bore and be sure the things you screw on the website is really as well. For those muzzle attachments, also ensure that the holes through which the bullet passes through are dead true to the bore. Many aftermarket screw-on everything is not good that way. Something that vents gas should vent symmetrically (i.e. whether it vents left, it must vent equally right, and likewise, whether it vents up, it should vent down equally). Uneven venting of gas can wreck accuracy.
14. Quality Ammunition: Ammo is a whole story itself, but loads which can be too hot typically shoot poorly in AR-15 complete upper. If you wish accuracy away from an AR-15, avoid overly hot loads. Shown below are test groups shot with four (4) different uppers, all with moderate loads. These four uppers all pretty much had a similar features and things done to them as explained on this page, and they also all shot great.