Inside our Shooters’ Forum, one member recently asked: “What makes an AR accurate? What parts with an AR really can affect accuracy – for example free-floating handguards, barrels, bolts, bolt carriers?” He wanted a truthful, well-informed answer, not merely sales pitches. Robert Whitley posted a very comprehensive solution to this question, depending on his experience building and testing many 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 a AR to improve consistent accuracy, and I use the words “consistent accuracy” because consistency is an integral part of it (i.e. lots of guns can give a few great 5-shot groups, but won’t do a really good 10- or 20-shot groups, plus some guns will shoot great some day and never so good on others).
Here are 14 key things we think are important to accuracy.
1. Great Barrel: You’ll require a premium match-grade barrel, well-machined with an excellent crown as well as a match-type chambering, true on the bore and well cut. The extension threads also must be cut true for the bore, with everything else true and then in proper alignment.
2. Rigid Upper: A rigid, heavy-walled upper receiver aids accuracy. The common AR upper receiver is made to get a lightweight carry rifle and so they stripped every one of the metal they might off it to really make it light to transport (which happens to be advantageous for that military). The world wide web result are upper receivers that are so thin you can flex all of them with your bare hands. These flexible uppers are “strong enough” for general use, however they are not suitable for accuracy. Accuracy improves 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 point yet it is always best to keep everything related to the barrel and the bore in complete alignment together with the bore (i.e. barrel extension, bolt, upper receiver, carrier, etc.).
4. Barrel Extension: You must Loctite or glue the barrel extension in the upper receiver. This holds it into position completely front to during the upper receiver. Otherwise if you have any play (and there typically is) it simply hangs around the face in the upper receiver completely dependent on the face of the upper receiver since the sole method to obtain support to the barrel instead of being made more a fundamental part of the upper receiver by being glued-in.
AR-X AR15 Upper5. Gas Block: You want a gas block that fails to impose pointed stress about the barrel. Clamp-on types that grab all the way up across the barrel are excellent. The blocks which can be pinned up with tapered pins that wedge against the barrel or perhaps the slip on form of block with set screws that push up from underneath (or directly on the barrel) can deform the bore within the barrel and may wreck the accuracy of any otherwise great barrel.
6. Free-Float Handguard: A rigid, free-float handguard (and so i emphasize the term rigid) really makes a difference. There are many types of free-float handguards along with a free-float handguard is, in as well as itself, a huge improvement over a non-free-float setup, but best can be a rigid set-up. A few of the ones 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 most beneficial since ARs wish to jump, bounce and twist when you let a try go, because the carrier actually starts to begin its cycle just before the bullet exits the bore.
7. Barrel Contour: You would like some meat around the barrel. In between the upper receiver and also the gas block don’t go real thin by using a barrel (we like 1? diameter if it’s workable weight-wise). When 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 gives vibrations and stress about the barrel, especially between the gas block returning to the receiver. A heavier barrel here dampens that. Staying a little heavier with barrel contour from the gas block area and in the market to the muzzle is good for a similar reasons. ARs possess a lot happening when you touch off a round and also the gas system pressures up along with the carrier starts moving (all prior to the bullet exits the bore) therefore the more situations are made heavier and rigid to counteract that this better – within reason (I’m not advocating a 12-lb barrel).
8. Gas Tube Routing Clearance: You desire a gas tube that runs freely throughout the barrel nut, with the front in the upper receiver, and thru the gas key from the carrier. Ensure the gas tube is not impinged by some of them, so it does not load the carrier inside a stressed orientation. You don’t want the gas tube bound up so that if the gas tube pressures up it immediately wants to transmit more force and impulse towards the barrel than would normally occur. We sometimes spend a 63dexjpky of 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 obtain them right – factory tubes may work OK nonetheless they typically do not function optimally without hand-fitting.
9. Gas Port Tuning: You need to avoid over-porting the gas port. Being over-gassed makes the gas system pressure up earlier and a lot more aggressively. This leads to more impulse, and increases forces and vibration affecting the very best end along with the barrel. Tune the gas port to give the amount of pressure required to function properly and adequately but you can forget.
10. Front/Back Bolt Play: If accuracy will be the game, don’t leave a lot of front/back bolt play (ensure that it stays .003? but a maximum of .005?). We’ve seen factory rifles run .012? to .015? play, that is OK if you wish to leave room for dirt and grime within a military application. However, that volume of play is not really well suited for a higher-accuracy AR build. Plenty of front/back bolt play allows rounds to be hammered in to the chamber and in reality re-formed in a non-consistent way, as they are loaded into the chamber.
11. Component Quality: Use good parts from a reputable source and be cautious about “gun show specials”. All parts are certainly not exactly the same. Some are excellent, some are certainly not so great, and several aftermarket parts are simply bad. Don’t hesitate to make use of mil-spec-type carriers; by and large they can be good for an accuracy build. Also, keep in mind that simply because a carrier says “National Match” or something that is else upon it does not necessarily mean it’s any better. Be skeptical of chrome-plated parts as being the chrome plating may change the parts dimensionally and might also make it hard to do hand-fitting for fit and function.
12. Upper to Lower Fit: A great upper/lower fit is effective. For quick and dirty fit enhancement, an Accu-Wedge in the rear helps a great deal. The supreme option would be to sleep the top to a specific lower in order that the lower and upper, when together, are definitely more like one integral unit. For the upper receivers we produce, we attempt to have the specs as near while we can, but still fit the numerous lowers on the market place.
13. Muzzle Attachments: Don’t screw in the muzzle (literally). Leave just as much metal on the barrel at the muzzle that you can. People like to thread the muzzle for a flash hider, suppressor, muzzle brake, as well as other attachment, but if you want accuracy, leave as much metal as possible there. And, in case you have something which screws on, set it up up so it can be put on and get it stay there without putting a lot of torque and stress onto it right where bullet exits the bore. If you are intending to thread the end in the barrel, help it become concentric with all the bore and be sure what you screw on the website is really as well. For many muzzle attachments, also be sure that the holes in which the bullet passes through are dead true for the bore. Many aftermarket screw-on the situation is not good like that. Anything that vents gas should vent symmetrically (i.e. when it vents left, it will 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 really a whole story itself, but loads that are too hot typically shoot poorly in best AR15 stock. If you want accuracy from an AR-15, avoid overly hot loads. Shown below are test groups shot with four (4) different uppers, all with moderate loads. These four uppers all just about had exactly the same features and things completed to them as explained in this post, and they all shot great.