Inside our Shooters’ Forum, one member recently asked: “What makes an AR accurate? What parts with an AR really can affect accuracy – like free-floating handguards, barrels, bolts, bolt carriers?” He wanted a sincere, well-informed answer, not simply sales pitches. Robert Whitley posted a really comprehensive answer to this question, based upon his experience building and testing a large number of AR-15 upper receiver for sale. Robert runs AR-X Enterprises, which produces match-grade uppers for High Power competitors, tactical shooters, and varminters.
There are plenty of things which can be done to a AR to improve consistent accuracy, and so i use the words “consistent accuracy” because consistency is an element of it (i.e. lots of guns will provide a few great 5-shot groups, but won’t do an excellent 10- or 20-shot groups, and a few guns will shoot great some day and not so great on others).
Here are 14 key things we believe are important to accuracy.
1. Great Barrel: You’ll require a premium match-grade barrel, well-machined with a great crown as well as a match-type chambering, true on the bore and well cut. The extension threads also needs to be cut true to the bore, with everything true as well as in proper alignment.
2. Rigid Upper: A rigid, heavy-walled upper receiver aids accuracy. The typical AR upper receiver was created for the lightweight carry rifle and so they stripped each of the metal they might off it making it light to hold (which can be advantageous for that military). The internet result are upper receivers which are so thin you can flex them with your bare hands. These flexible uppers are “strong enough” for general use, but are not perfect for accuracy. Accuracy improves by using a more rigid upper receiver.
3. True Receiver Face: We’ve discovered that truing the receiver face is valuable. Some may argue this time however it is always advisable to keep everything associated with the barrel and also the bore in complete alignment using the bore (i.e. barrel extension, bolt, upper receiver, carrier, etc.).
4. Barrel Extension: You ought to Loctite or glue the barrel extension into the upper receiver. This holds it in place entirely front to back in the upper receiver. Otherwise when there is any play (where there typically is) it simply hangs on the face of your upper receiver completely dependent on your face of the upper receiver as being the sole supply of support to the barrel rather than being made more a fundamental part of the upper receiver when you are glued-in.
AR-X AR15 Upper5. Gas Block: You want a gas block that does not impose pointed stress on the barrel. Clamp-on types that grab all the way up round the barrel are great. The blocks which are pinned up with tapered pins that wedge versus the barrel or maybe the slip on kind of block with set screws that push up from underneath (or right on the barrel) can deform the bore inside the barrel and will wreck the accuracy of an otherwise great barrel.
6. Free-Float Handguard: A rigid, free-float handguard (and I emphasize the word rigid) really makes a difference. There are lots of forms of free-float handguards as well as a free-float handguard is, in as well as itself, a huge improvement more than a non-free-float create, but best can be a rigid set-up. Some of the ones available on the market are small diameter, thin and/or flexible and should you be shooting off any kind of rest, bipod, front bag, etc., a rigid fore-end is better since ARs would like to jump, bounce and twist whenever you let a go go, because the carrier begins to begin its cycle ahead of the bullet exits the bore.
7. Barrel Contour: You desire some meat around the barrel. Between your upper receiver along with the gas block don’t go real thin having a barrel (we love 1? diameter if it’s workable weight-wise). When you touch off a round as well as the bullet passes the gas port, the gas system immediately starts pressuring on top of a gas impulse that provides vibrations and stress about the barrel, especially between the gas block back to the receiver. A heavier barrel here dampens that. Staying just a little heavier with barrel contour with the gas block area and to the muzzle is good for a similar reasons. ARs have a lot happening when you touch off a round as well as the gas system pressures up and the carrier starts moving (all ahead of the bullet exits the bore) and so the more the situation is 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 will want gas tube that runs freely with the barrel nut, from the front of your upper receiver, and thru the gas key in the carrier. Ensure that the gas tube is not really impinged by any one of them, so that it fails to load the carrier in the stressed orientation. You don’t want the gas tube bound up to ensure as soon as the gas tube pressures up it immediately wishes 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 get proper clearance and alignment. Most gas tubes do need a little “tweaking” to have them right – factory tubes may work OK but they typically tend not to function optimally without hand-fitting.
9. Gas Port Tuning: You want to avoid over-porting the gas port. Being over-gassed helps make the gas system pressure up earlier and more aggressively. This causes more impulse, and increases forces and vibration affecting the most notable end along with the barrel. Tune the gas port to present the level of pressure needed to function properly and adequately but no more.
10. Front/Back Bolt Play: If accuracy will be the game, don’t leave a lot of front/back bolt play (ensure that is stays .003? but not more than .005?). We’ve seen factory rifles run .012? to .015? play, which happens to be OK if you want to leave room for dirt and grime in a military application. However, that amount of play is not well suited for a high-accuracy AR build. A lot of front/back bolt play allows rounds being hammered in to the chamber and re-formed in a non-consistent way, since they are loaded in to the chamber.
11. Component Quality: Use good parts from a reputable source and become wary of “gun show specials”. All parts are certainly not exactly the same. Some are great, some usually are not so good, plus some aftermarket parts are merely bad. Don’t be scared to work with mil-spec-type carriers; in general they may be good for an accuracy build. Also, keep in mind that even though a carrier says “National Match” or something that is else onto it does not always mean it’s any better. Be suspicious of chrome-plated parts as the chrome plating can change the various components dimensionally and can also ensure it is hard to do hand-fitting for fit and function.
12. Upper to Lower Fit: An excellent upper/lower fit is helpful. For fast and dirty fit enhancement, an Accu-Wedge in the rear helps a whole lot. The ultimate option is to sleep the top to your specific lower so that the lower and upper, when together, are more like one integral unit. For the upper receivers we produce, we try to have the specs as near since we can, but nonetheless fit the different lowers in the market place.
13. Muzzle Attachments: Don’t screw in the muzzle (literally). Leave just as much metal on the barrel in the muzzle as you can. People want 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 as possible there. And, in case you have something which screws on, set it up up in order that it may be placed on and get it stay there without putting lots of torque and stress into it right the location where the bullet exits the bore. If you are going to thread the final of your barrel, allow it to be concentric using the bore and be sure everything you screw on the website can be as well. For many muzzle attachments, also be sure that the holes through which the bullet passes through are dead true for the bore. Many aftermarket screw-on things are not too good doing this. Anything that vents gas should vent symmetrically (i.e. whether it vents left, it must vent equally right, and likewise, whether it vents up, it must vent down equally). Uneven venting of gas can wreck accuracy.
14. Quality Ammunition: Ammo is actually a whole story on its own, but loads which can be too hot typically shoot poorly in AR15 collapsible stock. If you wish accuracy 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 done to them as explained in this post, and so they all shot great.