In your Shooters’ Forum, one member recently asked: “What makes an AR accurate? What parts by using an AR really can affect accuracy – such as free-floating handguards, barrels, bolts, bolt carriers?” He wanted a truthful, well-informed answer, not merely sales pitches. Robert Whitley posted an incredibly comprehensive response to this question, based upon his experience building and testing a large number of best AR-15 manufacturer. 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 to an AR to improve consistent accuracy, and I take advantage of the words “consistent accuracy” because consistency is a part of it (i.e. lots of guns will offer a few great 5-shot groups, but won’t do a really good 10- or 20-shot groups, plus some guns will shoot great a day and never so good on others).
Listed below are 14 key things we believe are crucial to accuracy.
1. Great Barrel: You’ll require a premium match-grade barrel, well-machined with a decent crown as well as a match-type chambering, true for the bore and well cut. The extension threads also needs to be cut true for the bore, with everything true and then in proper alignment.
2. Rigid Upper: A rigid, heavy-walled upper receiver aids accuracy. The standard AR upper receiver was developed for any lightweight carry rifle and so they stripped all the metal they may off it making it light to carry (which is advantageous for that military). The net result are upper receivers that are so thin you may flex them your bare hands. These flexible uppers are “strong enough” for general use, however are not suitable 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 point however it is always best to keep everything related to the barrel as well as 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 into the upper receiver. This holds it set up entirely front to in the upper receiver. Otherwise if there is any play (there typically is) it just hangs in the face in the upper receiver completely reliant on the face area from the upper receiver because the sole method to obtain support for that barrel in contrast to being made more a fundamental part of top of the receiver because they are glued-in.
AR-X AR15 Upper5. Gas Block: You desire a gas block that will not impose pointed stress around the barrel. Clamp-on types that grab all the way throughout the barrel are fantastic. The blocks which are pinned on with tapered pins that wedge up against the barrel or maybe the slip on type of block with set screws that push up from underneath (or right on the barrel) can deform the bore inside the barrel and might wreck the accuracy of your otherwise great barrel.
6. Free-Float Handguard: A rigid, free-float handguard (and so i emphasize the term rigid) really is important. There are numerous forms of free-float handguards as well as a free-float handguard is, in and of itself, an enormous improvement over a non-free-float put in place, but best can be a rigid set-up. Some of the ones out there are small diameter, thin or flexible and when you are shooting off any sort of rest, bipod, front bag, etc., a rigid fore-end is best since ARs want to jump, bounce and twist once you let a shot go, because the carrier starts to begin its cycle before the bullet exits the bore.
7. Barrel Contour: You need some meat about the barrel. Involving the upper receiver as well as the gas block don’t go real thin by using 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 up with a gas impulse which offers vibrations and stress around the barrel, especially in between the gas block to the receiver. A heavier barrel here dampens that. Staying a little bit heavier with barrel contour throughout the gas block area and over to the muzzle will work for a similar reasons. ARs use a lot occurring once you touch off a round as well as the gas system pressures up and also the carrier starts moving (all before the bullet exits the bore) therefore the more everything is made heavier and rigid to counteract how 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, throughout the front in the upper receiver, and through the gas key from the carrier. Ensure the gas tube is not really impinged by some of them, so that it is not going to load the carrier in a stressed orientation. You don’t want the gas tube bound up so that if 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 time moving the gas block with gas tube off and on new build uppers and tweaking gas tubes to have proper clearance and alignment. Most gas tubes do need some “tweaking” to obtain 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 makes the gas system pressure up earlier plus more aggressively. This will cause more impulse, and increases forces and vibration affecting the top end and the barrel. Tune the gas port to offer the amount of pressure necessary to function properly and adequately but you can forget.
10. Front/Back Bolt Play: If accuracy is 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 wish to leave room for grime and dirt inside a military application. However, that level of play is just not suitable for a high-accuracy AR build. Lots of front/back bolt play allows rounds to become hammered into the chamber and re-formed in a non-consistent way, since they are loaded in the chamber.
11. Component Quality: Use good parts from the reputable source and become wary of “gun show specials”. All parts usually are not the same. Some are excellent, some usually are not so excellent, and several aftermarket parts are simply bad. Don’t be scared to work with mil-spec-type carriers; in general they can be good for an accuracy build. Also, understand that simply because a carrier says “National Match” or something else on it does not always mean it’s any better. Be wary of chrome-plated parts as being the chrome plating can change the parts dimensionally and may also make it hard to do hand-fitting for fit and function.
12. Upper to Lower Fit: A good upper/lower fit helps. For fast and dirty fit enhancement, an Accu-Wedge in the rear helps a lot. The supreme solution is to sleep the top into a specific lower in order that the upper and lower, when together, are definitely more like one integral unit. For that upper receivers we produce, we attempt to obtain the specs as close since we can, but nevertheless fit the many lowers in the marketplace place.
13. Muzzle Attachments: Don’t screw within the muzzle (literally). Leave the maximum amount of metal in the barrel with the muzzle as you can. People like to thread the muzzle for the flash hider, suppressor, muzzle brake, or some other attachment, however, if you truly want accuracy, leave just as much metal as you can there. And, in case you have something which screws on, set it up so it can be used on and also have it stay there without putting plenty of torque and stress into it right where the bullet exits the bore. If you are going to thread the end in the barrel, make it concentric with all the bore and make certain the things you screw on there is just as well. For those muzzle attachments, also ensure 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 this way. Everything that vents gas should vent symmetrically (i.e. if this vents left, it ought to vent equally right, and likewise, whether it vents up, it will vent down equally). Uneven venting of gas can wreck accuracy.
14. Quality Ammunition: Ammo can be a whole story on its own, but loads which are too hot typically shoot poorly in best AR15 collapsible stock. If you would like accuracy away 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 article, and they also all shot great.