In your Shooters’ Forum, one member recently asked: “What makes an AR accurate? What parts by using an AR can really affect accuracy – including free-floating handguards, barrels, bolts, bolt carriers?” He wanted an honest, well-informed answer, not only sales pitches. Robert Whitley posted a really comprehensive reply to this query, based upon his experience building and testing a large number of AR-15 upper receiver. Robert runs AR-X Enterprises, which produces match-grade uppers for High 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 an integral part of it (i.e. a good amount of guns can give a few great 5-shot groups, but won’t do a really good 10- or 20-shot groups, and a few guns will shoot great one day and not so great on others).
Allow me to share 14 key things we think are important to accuracy.
1. Great Barrel: You’ll require a premium match-grade barrel, well-machined with a decent crown and a match-type chambering, true to the bore and well cut. The extension threads also must be cut true to the bore, with everything true and also in proper alignment.
2. Rigid Upper: A rigid, heavy-walled upper receiver aids accuracy. The common AR upper receiver was made for any lightweight carry rifle and they also stripped all of the metal they may off it so it will be light to hold (which happens to be advantageous for the 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, however are not suitable for accuracy. Accuracy improves by using a more rigid upper receiver.
3. True Receiver Face: We’ve found out that truing the receiver face is valuable. Some may argue this aspect however it is always better to keep everything relevant to 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 must Loctite or glue the barrel extension to the upper receiver. This holds it set up completely front to back into the upper receiver. Otherwise if there is any play (there typically is) it really hangs around the face in the upper receiver completely determined by the face area from the upper receiver because the sole method to obtain support for the barrel instead of being made more an important part of the top receiver when you are glued-in.
AR-X AR15 Upper5. Gas Block: You need a gas block that does not impose pointed stress on the barrel. Clamp-on types that grab entirely around the barrel are perfect. The blocks that are pinned up with tapered pins that wedge versus the barrel or perhaps the slip on kind 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 accuracy of an otherwise great barrel.
6. Free-Float Handguard: A rigid, free-float handguard (and I emphasize the term rigid) really is important. There are numerous types of free-float handguards along with a free-float handguard is, in and of itself, an enormous improvement more than a non-free-float set up, but best is actually a rigid set-up. Some of the ones out there are small diameter, thin and/or flexible and in case you are shooting off any sort of rest, bipod, front bag, etc., a rigid fore-end is better since ARs desire to jump, bounce and twist whenever you let a go go, since the carrier starts to begin its cycle prior to the bullet exits the bore.
7. Barrel Contour: You desire some meat about the barrel. In 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). Whenever you touch off a round and the bullet passes the gas port, the gas system immediately starts pressuring track of a gas impulse that offers vibrations and stress about the barrel, especially involving the gas block back 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 will work for the identical reasons. ARs have a lot occurring once you touch off a round as well as the gas system pressures up as well as the carrier starts moving (all before the bullet exits the bore) hence the more things are made heavier and rigid to counteract 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 from the barrel nut, from the front in the upper receiver, and through the gas key inside the carrier. Ensure the gas tube will not be impinged by some of them, in order that it is not going to load the carrier in the stressed orientation. You don’t want the gas tube bound up in order that if the gas tube pressures up it immediately wishes to transmit more force and impulse to the barrel than would normally occur. We sometimes spend a 63dexjpky of energy moving the gas block with gas tube on and off new build uppers and tweaking gas tubes to have proper clearance and alignment. Most gas tubes do need a little “tweaking” to get them right – factory tubes may work OK however they typically usually do not function optimally without hand-fitting.
9. Gas Port Tuning: You wish to avoid over-porting the gas port. Being over-gassed helps to make the gas system pressure up earlier and a lot more aggressively. This leads to more impulse, and increases forces and vibration affecting the top end and also the barrel. Tune the gas port to offer the volume of pressure found it necessary to function properly and adequately but no more.
10. Front/Back Bolt Play: If accuracy is definitely the game, don’t leave lots of front/back bolt play (keep it .003? but at most .005?). We’ve seen factory rifles run .012? to .015? play, that is OK if you want to leave room for grime and dirt inside a military application. However, that amount of play is not really ideal for an increased-accuracy AR build. Lots of front/back bolt play allows rounds to be hammered to the chamber and also re-formed in the non-consistent way, since they are loaded in to the chamber.
11. Component Quality: Use good parts from the reputable source and become wary of “gun show specials”. All parts are NOT a similar. Some are excellent, some are certainly not so great, and some aftermarket parts are merely bad. Don’t be scared to utilize mil-spec-type carriers; in general they can be good for an accuracy build. Also, remember that just because a carrier says “National Match” or something else onto it does not necessarily mean it’s any better. Be suspicious of chrome-plated parts because the chrome plating can transform the parts dimensionally and will also make it hard to do hand-fitting for fit and performance.
12. Upper to lessen Fit: An effective upper/lower fit is helpful. For quick and dirty fit enhancement, an Accu-Wedge within the rear helps a great deal. The ultimate solution is to sleep top of the into a specific lower so that the upper and lower, when together, tend to be more like one integral unit. For that upper receivers we produce, we attempt to get the specs as close when we can, but nonetheless fit the different lowers in the market place.
13. Muzzle Attachments: Don’t screw within the muzzle (literally). Leave as much metal in the barrel at the muzzle as you can. People want to thread the muzzle for a flash hider, suppressor, muzzle brake, as well as other attachment, however if you really want accuracy, leave the maximum amount of metal since you can there. And, for those who have an issue that screws on, set it up to ensure that it can be put on and also have it stay there without putting lots of torque and stress upon it right in which the bullet exits the bore. If you are planning to thread the conclusion of the barrel, make it concentric with all the bore and ensure the things you screw on the website can be as well. For all muzzle attachments, also be sure that the holes in which the bullet passes through are dead true on the bore. Many aftermarket screw-on the situation is not so good that way. Anything that vents gas should vent symmetrically (i.e. if this vents left, it should vent equally right, and likewise, if it vents up, it should vent down equally). Uneven venting of gas can wreck accuracy.
14. Quality Ammunition: Ammo is a whole story on its own, but loads that are too hot typically shoot poorly in best AR-15 barrel. If you would like accuracy out of 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 virtually had exactly the same features and things performed to them as explained in this article, and so they all shot great.