In your Shooters’ Forum, one member recently asked: “What makes an AR accurate? What parts on an AR can really affect accuracy – such as free-floating handguards, barrels, bolts, bolt carriers?” He wanted a truthful, well-informed answer, not only sales pitches. Robert Whitley posted a very comprehensive response to this, based upon his experience building and testing dozens of AR-15 complete upper. Robert runs AR-X Enterprises, which produces match-grade uppers for top Power competitors, tactical shooters, and varminters.
There are a variety of things that you can do to an AR to further improve consistent accuracy, and I use the words “consistent accuracy” because consistency is an integral part of it (i.e. a good amount of guns will give a few great 5-shot groups, but won’t do a good 10- or 20-shot groups, and some guns will shoot great some day rather than so great on others).
Here are 14 key things we think are important to accuracy.
1. Great Barrel: You’ll need a premium match-grade barrel, well-machined with a good crown and a match-type chambering, true towards the bore and well cut. The extension threads should also be cut true on the bore, with everything else true and then in proper alignment.
2. Rigid Upper: A rigid, heavy-walled upper receiver aids accuracy. The standard AR upper receiver was created for a lightweight carry rifle plus they stripped all of the metal they may off it so it will be light to transport (which can be advantageous to the military). The world wide web result are upper receivers that are so thin it is possible to flex them your bare hands. These flexible uppers are “strong enough” for general use, however are not suitable for accuracy. Accuracy improves with a more rigid upper receiver.
3. True Receiver Face: We’ve found that truing the receiver face is valuable. Some may argue this point yet it is always advisable to keep everything associated with 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 the upper receiver. This holds it into position all the way front to in the upper receiver. Otherwise if you find any play (and then there typically is) it just hangs around the face in the upper receiver completely influenced by your face in the upper receiver because the sole supply of support for the barrel instead of being made more an integral part of the top receiver by being glued-in.
AR-X AR15 Upper5. Gas Block: You want a gas block that does not impose pointed stress in the barrel. Clamp-on types that grab completely round the barrel are great. The blocks that are pinned up with tapered pins that wedge against the barrel or maybe the slip on type of block with set screws that push up from underneath (or entirely on the barrel) can deform the bore inside the barrel and can wreck the precision of the otherwise great barrel.
6. Free-Float Handguard: A rigid, free-float handguard (and so i emphasize the term rigid) really is important. There are lots of forms of free-float handguards and a free-float handguard is, in and of itself, a massive improvement more than a non-free-float create, but best can be a rigid set-up. Several of the ones out there are small diameter, thin and/or flexible and when you are shooting off almost any rest, bipod, front bag, etc., a rigid fore-end is best since ARs desire to jump, bounce and twist when you let a try go, because the carrier starts to begin its cycle before the bullet exits the bore.
7. Barrel Contour: You desire some meat on the barrel. Between the upper receiver and the gas block don’t go real thin by using a barrel (we like 1? diameter if it’s workable weight-wise). If you touch off a round as well as the bullet passes the gas port, the gas system immediately starts pressuring track of a gas impulse that provides vibrations and stress about the barrel, especially involving the gas block back to the receiver. A heavier barrel here dampens that. Staying a little heavier with barrel contour with the gas block area and in the market to the muzzle is useful for the same reasons. ARs possess a lot taking place if you touch off a round and also the gas system pressures up and also the carrier starts moving (all just before the bullet exits the bore) hence the more things 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 will want gas tube that runs freely with the barrel nut, with the front from the upper receiver, and thru the gas key inside the carrier. Guarantee the gas tube is just not impinged by any one of them, to ensure 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 when 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 your time moving the gas block with gas tube on / off new build uppers and tweaking gas tubes to obtain proper clearance and alignment. Most gas tubes do need some “tweaking” to have them right – factory tubes may work OK however they typically usually do not 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 will cause more impulse, and increases forces and vibration affecting the top end and the barrel. Tune the gas port to present the amount of pressure required to function properly and adequately but no longer.
10. Front/Back Bolt Play: If accuracy is definitely the game, don’t leave a great deal 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 need to leave room for dirt and grime in the military application. However, that volume of play will not be perfect for a high-accuracy AR build. A lot of front/back bolt play allows rounds to become hammered in to the chamber and in reality re-formed within a non-consistent way, as they are loaded to the chamber.
11. Component Quality: Use good parts from a reputable source and stay cautious about “gun show specials”. All parts will not be the identical. Some are great, some will not be so great, plus some aftermarket parts are merely bad. Don’t be scared to work with mil-spec-type carriers; by and large they can be good for an accuracy build. Also, keep in mind that even though a carrier says “National Match” or something else onto it does not always mean it’s any better. Be skeptical of chrome-plated parts since the chrome plating can alter the various components dimensionally and can also make it difficult to do hand-fitting for fit and performance.
12. Upper to reduce Fit: A good upper/lower fit helps. For quick and dirty fit enhancement, an Accu-Wedge from the rear helps a lot. The supreme option is to sleep top of the into a specific lower so that the upper and lower, when together, are definitely more like one integral unit. For the upper receivers we produce, we try to obtain the specs as near since we can, but nonetheless fit the various lowers in the marketplace place.
13. Muzzle Attachments: Don’t screw up the muzzle (literally). Leave all the metal in the barrel with the muzzle as possible. People prefer to thread the muzzle for the flash hider, suppressor, muzzle brake, as well as other attachment, however, if you really want accuracy, leave as much metal as possible there. And, if you have an issue that screws on, set it up up so that it may be put on and have it stay there without putting a great deal of torque and stress on it right in which the bullet exits the bore. If you are intending to thread the final from the barrel, make it concentric using the bore and make sure the things you screw on the website is really as well. For those muzzle attachments, also be sure that the holes through which the bullet passes through are dead true to the bore. Many aftermarket screw-on situations are not good doing this. Anything that vents gas should vent symmetrically (i.e. if this vents left, it must vent equally right, and likewise, when 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 on its own, but loads which are too hot typically shoot poorly in AR15 upper receiver. If you want accuracy from 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 basically had exactly the same features and things done to them as explained in the following paragraphs, plus they all shot great.