In our Shooters’ Forum, one member recently asked: “What makes an AR accurate? What parts by using an AR can definitely affect accuracy – for example free-floating handguards, barrels, bolts, bolt carriers?” He wanted an honest, well-informed answer, not merely sales pitches. Robert Whitley posted a really comprehensive response to this query, according to his experience building and testing many how to install an upper receiver. Robert runs AR-X Enterprises, which produces match-grade uppers for top Power competitors, tactical shooters, and varminters.
There are plenty of things that can be done to an AR to enhance consistent accuracy, and I make use of the words “consistent accuracy” because consistency is a part of it (i.e. plenty of guns will give a couple of great 5-shot groups, but won’t do an excellent 10- or 20-shot groups, and a few guns will shoot great some day instead of so good on others).
Listed here are 14 key things we believe are very 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 on the bore and well cut. The extension threads also needs to be cut true for the bore, with everything else true as well as in proper alignment.
2. Rigid Upper: A rigid, heavy-walled upper receiver aids accuracy. The standard AR upper receiver was developed for the lightweight carry rifle plus they stripped all the metal they could off it making it light to hold (which is advantageous for that military). The internet result are upper receivers which are so thin you may flex these with your bare hands. These flexible uppers are “strong enough” for general use, but they are not ideal for accuracy. Accuracy improves having a more rigid upper receiver.
3. True Receiver Face: We’ve learned that truing the receiver face is valuable. Some may argue this aspect however it is always wise to keep everything relevant to the barrel and the bore in complete alignment using the bore (i.e. barrel extension, bolt, upper receiver, carrier, etc.).
4. Barrel Extension: You must Loctite or glue the barrel extension to the upper receiver. This holds it in position entirely front to during the upper receiver. Otherwise if there is any play (and there typically is) it merely hangs in the face of your upper receiver completely reliant on the face area of the upper receiver since the sole source of support for your barrel instead of being made more an important part of top of the receiver by being glued-in.
AR-X AR15 Upper5. Gas Block: You will want gas block that fails to impose pointed stress on the barrel. Clamp-on types that grab all the way up round the barrel are excellent. The blocks which are pinned on with tapered pins that wedge versus the barrel or even the slip on form of block with set screws that push up from underneath (or entirely on the barrel) can deform the bore inside of the barrel and can wreck the precision of the otherwise great barrel.
6. Free-Float Handguard: A rigid, free-float handguard (and i also emphasize the phrase rigid) really makes a difference. There are several varieties of free-float handguards and a free-float handguard is, in and also itself, a massive 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 or flexible and if you are shooting off almost any rest, bipod, front bag, etc., a rigid fore-end is better since ARs wish to jump, bounce and twist once you let a go go, because the carrier actually starts to begin its cycle just before the bullet exits the bore.
7. Barrel Contour: You desire some meat around the barrel. In between the upper receiver and the gas block don’t go real thin using a barrel (we love to 1? diameter if it’s workable weight-wise). If you touch off a round and the bullet passes the gas port, the gas system immediately starts pressuring up with a gas impulse that gives vibrations and stress on the barrel, especially between the gas block straight back to the receiver. A heavier barrel here dampens that. Staying a bit heavier with barrel contour from the gas block area and in the market to the muzzle is good for exactly the same reasons. ARs use a lot going on once you touch off a round and the gas system pressures up and the carrier starts moving (all prior to the bullet exits the bore) and so the more everything 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 through the barrel nut, through the front from the upper receiver, and through the gas key inside the carrier. Ensure that the gas tube is not really impinged by any of them, in order that it will not load the carrier in a stressed orientation. You don’t want the gas tube bound up to ensure 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 energy moving the gas block with gas tube on / off 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 nonetheless they typically tend not to function optimally without hand-fitting.
9. Gas Port Tuning: You wish to avoid over-porting the gas port. Being over-gassed definitely makes the gas system pressure up earlier plus more aggressively. This causes more impulse, and increases forces and vibration affecting the top end and also the barrel. Tune the gas port to offer the amount of pressure found it necessary to function properly and adequately but forget about.
10. Front/Back Bolt Play: If accuracy is the game, don’t leave a lot of front/back bolt play (keep it .003? but at most .005?). We’ve seen factory rifles run .012? to .015? play, which is OK if you wish to leave room for grime and dirt in the military application. However, that amount of play is not well suited for an increased-accuracy AR build. Lots of front/back bolt play allows rounds being hammered to the chamber and actually re-formed inside a non-consistent way, since they are loaded in the chamber.
11. Component Quality: Use good parts from a reputable source and stay cautious about “gun show specials”. All the parts usually are not a similar. Some are perfect, some will not be so great, and several aftermarket parts are simply just bad. Don’t be afraid to use mil-spec-type carriers; generally they may be good for an accuracy build. Also, do not forget that just because a carrier says “National Match” or something that is else upon it does not necessarily mean it’s any better. Be suspicious of chrome-plated parts as being the chrome plating can change the parts dimensionally and will also allow it to be hard to do hand-fitting for fit and performance.
12. Upper to reduce Fit: A great upper/lower fit is helpful. For quick and dirty fit enhancement, an Accu-Wedge in the rear helps a good deal. The best option would be to sleep the top to some specific lower in order that the upper and lower, when together, are definitely more like one integral unit. To the upper receivers we produce, we try to get the specs as near as we can, but still fit the many lowers in the marketplace place.
13. Muzzle Attachments: Don’t screw in the muzzle (literally). Leave just as much metal about the barrel on the muzzle that you can. People want to thread the muzzle for any flash hider, suppressor, muzzle brake, or some other attachment, but if you truly desire accuracy, leave just as much metal as possible there. And, in case you have a thing that screws on, set it up so that it can be used on and have it stay there without putting plenty of torque and stress on it right where bullet exits the bore. If you are intending to thread the final in the barrel, help it become concentric together with the bore and ensure the things you screw on there can be as well. For all those muzzle attachments, also ensure that the holes by which the bullet passes through are dead true for the bore. Many aftermarket screw-on things are not so good that way. Something that vents gas should vent symmetrically (i.e. if it vents left, it should vent equally right, and likewise, if it vents up, it ought to vent down equally). Uneven venting of gas can wreck accuracy.
14. Quality Ammunition: Ammo is actually a whole story itself, but loads which are too hot typically shoot poorly in AR15 2 stage trigger. If you need accuracy out of an AR-15, avoid overly hot loads. Shown listed below are test groups shot with four (4) different uppers, all with moderate loads. These four uppers all just about had the identical features and things carried out to them as explained in the following paragraphs, plus they all shot great.