July 18th, 2013

Building an Accurate AR — Robert Whitley Explains What Works

In our Shooters’ Forum, one member posed the question: “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 an honest, well-informed answer, not just sales pitches. Robert Whitley posted a very comprehensive answer to this question, based on his experience building and testing dozens of AR-platform rifles. Robert runs AR-X Enterprises, which produces match-grade uppers for High Power competitors, tactical shooters, and varminters.

AR-X AR15 Upper

Building an Accurate AR — What is Most Important

by Robert Whitley
There are a lot of things that can be done to an AR to enhance consistent accuracy, and I use the words “consistent accuracy” because consistency is a part of it (i.e. plenty of guns will give a couple great 5-shot groups, but won’t do a very good 10- or 20-shot groups, and some guns will shoot great one day and not so good on others).

Here are things we think are important to accuracy.

1. Great Barrel: You’ll want a premium match-grade barrel, well-machined with a good crown and a match-type chambering, true to the bore and well cut. The extension threads must also be cut true to the bore, with everything true and in proper alignment.

2. Rigid Upper: A rigid, heavy-walled upper receiver aids accuracy. The typical AR upper receiver was made for a lightweight carry rifle and they stripped all the metal they could off it to make it light to carry (which is advantageous for the military). The net result are upper receivers that are so thin you can flex them with your bare hands. These flexible uppers are “strong enough” for general use, but they are not ideal for accuracy. Accuracy improves with a more rigid upper receiver.

AR-X AR15 Upper

3. True Receiver Face: We’ve found that truing the receiver face is valuable. Some may argue this point but it is always best to keep everything related to the barrel and the bore in complete alignment with the bore (i.e. barrel extension, bolt, upper receiver, carrier, etc.).

4. Barrel Extension: You should Loctite or glue the barrel extension into the upper receiver. This holds it in place all the way front to back in the upper receiver. Otherwise if there is any play (and there typically is) it just hangs on the face of the upper receiver completely dependent on the face of the upper receiver as the sole source of support for the barrel as opposed to being made more an integral part of the upper receiver by being glued-in.

AR-X AR15 Upper5. Gas Block: You want a gas block that does not impose pointed stress on the barrel. Clamp-on types that grab all the way around the barrel are excellent. The blocks that are pinned on with tapered pins that wedge against the barrel or the slip on type of block with set screws that push up from underneath (or directly 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 word rigid) really makes a difference. There are many types of free-float handguards and a free-float handguard is, in and of itself, a huge improvement over a non-free-float set up, but best is a rigid set-up. Some of the ones on the market are small diameter, thin and/or flexible and if you are shooting off any type of rest, bipod, front bag, etc., a rigid fore-end is best since ARs want to jump, bounce and twist when you let a shot go, as the carrier starts to begin its cycle before the bullet exits the bore.

7. Barrel Contour: You want some meat on the barrel. Between the upper receiver and the gas block don’t go real thin with a barrel (we like 1″ diameter if it’s workable weight-wise). When you touch off a round and the bullet passes the gas port, the gas system immediately starts pressuring up with a gas impulse that provides vibrations and stress on the barrel, especially between the gas block back to the receiver. A heavier barrel here dampens that. Staying a little heavier with barrel contour through the gas block area and out to the muzzle is good for the same reasons. ARs have a lot going on when you touch off a round and the gas system pressures up and the carrier starts moving (all before the bullet exits the bore) so 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 want a gas tube that runs freely through the barrel nut, through the front of the upper receiver, and through the gas key in the carrier. Ensure the gas tube is not impinged by any of them, so that it does not load the carrier in a stressed orientation. You don’t want the gas tube bound up so that when the gas tube pressures up it immediately wants to transmit more force and impulse to the barrel than would normally occur. We sometimes spend a lot 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 a little “tweaking” to get them right — factory tubes may work OK but they typically do not 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 and more aggressively. This causes more impulse, and increases forces and vibration affecting the top end and the barrel. Tune the gas port to give the amount of pressure needed to function properly and adequately but no more.

10. Front/Back Bolt Play: If accuracy is the game, don’t leave a lot of front/back bolt play (keep it .003″ but no more than .005″). We’ve seen factory rifles run .012″ to .015″ play, which is OK if you need to leave room for dirt and grime in a military application. However, that amount of play is not ideal for a high-accuracy AR build. A lot of front/back bolt play allows rounds to be hammered into the chamber and actually 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 wary of “gun show specials”. All parts are NOT the same. Some are good, some are not so good, and some aftermarket parts are simply bad. Don’t be afraid to use mil-spec-type carriers; by and large they are excellent for an accuracy build. Also, remember that just because a carrier says “National Match” or something else on it does not necessarily mean it’s any better. Be wary of chrome-plated parts as the chrome plating can change the parts dimensionally and can also make it hard to do hand-fitting for fit and function.

AR-X AR15 Upper

12. Upper to Lower Fit: A good upper/lower fit is helpful. For quick and dirty fit enhancement, an Accu-Wedge in the rear helps a lot. The ultimate solution is to bed the upper to a specific lower so that the upper and lower, when together, are more like one integral unit. For the upper receivers we produce, we try to get the specs as close as we can, but still fit the various lowers in the market place.

13. Muzzle Attachments: Don’t screw up the muzzle (literally). Leave as much metal on the barrel at the muzzle as you can. People like to thread the muzzle for a flash hider, suppressor, muzzle brake, or some other attachment, but if you really want accuracy, leave as much metal as you can there. And, if you have something that screws on, set it up so that it can be put on and have it stay there without putting a lot of torque and stress on it right where the bullet exits the bore. If you are going to thread the end of the barrel, make it concentric with the bore and make sure what you screw on there is as well. For all muzzle attachments, also ensure that the holes through which the bullet passes through are dead true to the bore. Many aftermarket screw-on things are not so good that way. Anything that vents gas should vent symmetrically (i.e. if it 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 by itself, but loads that are too hot typically shoot poorly in an AR-15. If you want accuracy out of 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 pretty much had the same features and things done to them as explained in this article, and they all shot great.

AR-X AR15 Upper

Robert Whitley
www.6mmAR.com

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July 18th, 2013

Reloading for 3-Gun Competition — Practical Advice

three gun competitionThis article by Corey Swantz originally appeared in The Reloading Press, the Sinclair Int’l Blog.

Much less precision is required to get good scores in 3-gun competition than in strictly accuracy-oriented disciplines like F-Class or Benchrest. In 3-gun, [the game is] about hitting targets in the shortest amount of time, not how close to the center of the target you can get or how small the group can be. Ammunition that’s accurate to 1-2 MOA is more than sufficient for 3-gun competition, as the targets tend to be 4-6 MOA in size.

For my personal 3-gun load testing, I used three powders: Varget, IMR 8208 XBR, and Accurate 2230. All three powders gave me good results, but the 8208 XBR was the leader of the pack. I settled on a moderate charge that pushes a 73gr Berger BTHP at about 2,500 fps through my 16″-barreled AR15. While I’m sure I could obtain a higher velocity with these bullets, this speed yielded the best accuracy results in my initial testing with fully prepped brass.

With the high volume of ammunition that I need for 3-gun matches and practice, I wanted to eliminate as many case prep steps as possible and still end up with ammunition that was accurate enough for 3-gun. I fully prepped some once-fired brass from primer pocket to case mouth and everything in between. I also took some once-fired cases that had simply been trimmed to length, and loaded them without doing any other prep work. With these loads in hand, I headed out to the range to shoot some groups. Below are the results from my 200 yard group tests:

Prepped Brass Delivered Higher Score on Bullseye Target

3-gun reloading brass

As you can see from the photos, the groups yielded results along the lines of what I expected. The fully-prepped brass produced five 10s , whereas the un-prepped brass produced only two 10s, and both of those just touched the outer edge of the 10-ring.

However, the un-prepped brass kept all the shots inside the 8-ring, which is plenty precise for shooting the large targets used in 3-gun matches.

National Defense Match at Camp Perry
I decided to further test my un-prepped brass loads by shooting them in the National Defense Match (NDM) at Camp Perry and the Rockcastle 3-Gun Pro-Am Championship. At the NDM, the target used in the longer-range stages was a standard-size NRA Tombstone target, similar to the targets used in most 3-gun matches. Using the un-prepped brass loads, I was able to keep all my shots on the tombstone targets from 100-300 yards, and had only one miss from the 400-yard line. That one miss was my fault, as I jerked the trigger on the last shot, pulling it off to the left. Un-prepped brass held up quite well under Camp Perry NDM conditions.

Un-Prepped Good Enough for Class Win at Rockcastle 3-Gun Pro-Am Championship
Two weeks after the NDM, I traveled to Kentucky for the Rockcastle 3-Gun Pro-Am Championship. There were seven stages in this match, two of which required long-range rifle shots with my AR15. The longest stage of the match had eight steel targets sized from 4″ to 10″ in diameter, placed from 75 to 265 yards. My ammunition proved accurate enough at these distances to neutralize all the steel targets with single shots, something few other shooters were able to do. I finished over two seconds ahead of the nearest competitor on this stage and ended up winning the event. Clearly un-prepped brass was plenty good for the Rockcastle 3-Gun Pro Am, too!

Because of the results I’ve gotten on the practice range, and two very solid performances in competition last year, I feel confident that my loading process for the upcoming 3-Gun Nation Semi-Pro Series will consist of simply sizing and trimming brass, then loading it with my preferred recipe. While the fully prepped brass was indeed more accurate, the un-prepped brass loads were accurate enough to allow me to hit 3-gun targets . Now, I can take the time I save in the reloading room and spend it out on the practice range.

Corey Schwanz, Sinclair Reloading Technician

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July 18th, 2013

Portable Gun Rack Holds Long Guns in Vehicle Trunks

Creedmoor Sports is selling a new product that may be useful for folks who haul multiple rifles to the range. The new ScopeSaver Trunk Rack is a freestanding gun rack designed to hold one to four rifles or shotguns during transport. The rack can also be used to display guns and/or hold them during cleaning operations. The product is called a “ScopeSaver” because it allows scoped rifles to be transported upside-down, which provides more clearance for the scopes.

Each firearm rests in a pair of 3″-high, felt-covered U-shaped brackets (aka scounces). One sconce of each pair holds guns with thick stocks, and the other holds stocks that are thinner. Firearms can also be placed in the rack either right-side-up or upside-down depending on their shape. Depending on their size, some guns can also be placed in the rack while inside soft cases.

Creedmoor scopesaver trunk rackThe ScopeSaver Trunk rack holds four guns, is 23.5” deep, 23 7/8” wide, 13” high and is made of 10% fiberglass-filled polypropylene. It holds two large and two small oil/cleaning solution containers and multiple cleaning rods of different sizes. A special tapered-slot binding system allows several rods to be stored.

Reinforced carrying handles are built into the rack. The four corners of the rack are flat on the bottom, so adhesive-backed Velcro strips can be attached (which should grip on carpeted trunks). Additionally, you can insert tie-downs through slots in each of the four lower corner braces.

Creedmoor scopesaver trunk rack

Product tip from EdLongrange. We welcome reader submissions.
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