In your Shooters’ Forum, one member recently asked: “What makes an AR accurate? What parts with an AR really can affect accuracy – such as free-floating handguards, barrels, bolts, bolt carriers?” He wanted an honest, well-informed answer, not just sales pitches. Robert Whitley posted a really comprehensive response to this question, according to his experience building and testing a large number of AR-15 2 stage trigger. Robert runs AR-X Enterprises, which produces match-grade uppers for top Power competitors, tactical shooters, and varminters.
There are tons of things that you can do with an AR to improve consistent accuracy, and so i make use of the words “consistent accuracy” because consistency is an element of it (i.e. lots of guns will give a couple great 5-shot groups, but won’t do a very good 10- or 20-shot groups, and a few guns will shoot great one day instead of so great on others).
Here are 14 key things we think are very important to accuracy.
1. Great Barrel: You’ll want a premium match-grade barrel, well-machined with a great crown and a match-type chambering, true on the bore and well cut. The extension threads also must be cut true to the bore, with everything else true and in proper alignment.
2. Rigid Upper: A rigid, heavy-walled upper receiver aids accuracy. The normal AR upper receiver is made for any lightweight carry rifle and they stripped each of the metal they could off it making it light to carry (that is advantageous for your 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, however are not well suited for accuracy. Accuracy improves with a more rigid upper receiver.
3. True Receiver Face: We’ve learned that truing the receiver face is valuable. Some may argue this aspect yet it is always wise to keep everything related to the barrel and also the bore in complete alignment together with the bore (i.e. barrel extension, bolt, upper receiver, carrier, etc.).
4. Barrel Extension: You need to Loctite or glue the barrel extension to the upper receiver. This holds it set up all the way front to in the upper receiver. Otherwise when there is any play (and there typically is) it simply hangs in the face in the upper receiver completely influenced by the face in the upper receiver as the sole source of support for the barrel rather than being made more a fundamental part of the top receiver when you are glued-in.
AR-X AR15 Upper5. Gas Block: You will want gas block that does not impose pointed stress around the barrel. Clamp-on types that grab entirely across the barrel are excellent. The blocks which can be pinned up with tapered pins that wedge against the barrel or the slip on kind of block with set screws that push up from underneath (or right on the barrel) can deform the bore within the barrel and might wreck the precision of the otherwise great barrel.
6. Free-Float Handguard: A rigid, free-float handguard (and that i emphasize the saying rigid) really is important. There are many kinds of free-float handguards and a free-float handguard is, in and of itself, a huge improvement spanning a non-free-float setup, but best is a rigid set-up. Some of the ones on the market are small diameter, thin and flexible and should you be shooting off any sort of rest, bipod, front bag, etc., a rigid fore-end is advisable since ARs would like to jump, bounce and twist when you let a try go, as being the carrier actually starts to begin its cycle before the bullet exits the bore.
7. Barrel Contour: You need some meat in the barrel. Involving the upper receiver and also the gas block don’t go real thin having a barrel (we like 1? diameter if it’s workable weight-wise). Whenever you touch off a round and also the bullet passes the gas port, the gas system immediately starts pressuring track of a gas impulse that provides vibrations and stress around the barrel, especially between your gas block returning to the receiver. A heavier barrel here dampens that. Staying a bit heavier with barrel contour throughout the gas block area and to the muzzle will work for exactly the same reasons. ARs use a lot occurring whenever you touch off a round as well as the gas system pressures up and also the carrier starts moving (all just before the bullet exits the bore) so 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 desire a gas tube that runs freely through the barrel nut, throughout the front in the upper receiver, and through the gas key inside the carrier. Ensure the gas tube is not really impinged by any kind of them, so it is not going to load the carrier inside a stressed orientation. You don’t want the gas tube bound up so that as soon as 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 your time moving the gas block with gas tube on and off new build uppers and tweaking gas tubes to get proper clearance and alignment. Most gas tubes do need some “tweaking” to get them right – factory tubes may work OK however 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 to make the gas system pressure up earlier plus more aggressively. This leads to more impulse, and increases forces and vibration affecting the best end and the barrel. Tune the gas port to present the level of pressure found it necessary to function properly and adequately but no more.
10. Front/Back Bolt Play: If accuracy will be the game, don’t leave lots of front/back bolt play (keep it .003? but no more than .005?). We’ve seen factory rifles run .012? to .015? play, that is OK if you have to leave room for dirt and grime in the military application. However, that level of play is not really well suited for a very high-accuracy AR build. Lots of front/back bolt play allows rounds to be hammered into the chamber and re-formed in a non-consistent way, as they are loaded to the chamber.
11. Component Quality: Use good parts coming from a reputable source and stay cautious about “gun show specials”. All parts are certainly not exactly the same. Some are good, some are certainly not so great, and some aftermarket parts are just bad. Don’t hesitate to utilize mil-spec-type carriers; generally these are good for an accuracy build. Also, keep in mind that simply because a carrier says “National Match” or something that is else on it does not necessarily mean it’s any better. Be wary of chrome-plated parts as the chrome plating can alter the various components dimensionally and may also help it become hard to do hand-fitting for fit and performance.
12. Upper to lessen Fit: An excellent upper/lower fit is helpful. For fast and dirty fit enhancement, an Accu-Wedge inside the rear helps a whole lot. The ultimate option would be to sleep top of the to some specific lower to ensure the upper and lower, when together, will be more like one integral unit. For your upper receivers we produce, we try to have the specs as close when we can, but nevertheless fit the numerous lowers in the market place.
13. Muzzle Attachments: Don’t screw up the muzzle (literally). Leave just as much metal on the barrel with the muzzle since you can. People prefer to thread the muzzle for the flash hider, suppressor, muzzle brake, as well as other attachment, but if you truly desire accuracy, leave the maximum amount of metal as you can there. And, for those who have something that screws on, set it up up so it can be put on and possess it stay there without putting lots of torque and stress into it right in which the bullet exits the bore. If you are intending to thread the conclusion of your barrel, make it concentric with the bore and make sure what you screw on the website is as well. For all muzzle attachments, also be sure that the holes by which the bullet passes through are dead true towards the bore. Many aftermarket screw-on the situation is not too good doing this. Whatever vents gas should vent symmetrically (i.e. when it vents left, it will 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 a whole story on its own, but loads that are too hot typically shoot poorly in cheap AR-15 uppers for sale. If you need 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 the identical features and things done to them as explained in this article, plus they all shot great.