In June 2020, Hornady introduced the 6mm ARC, a new SAAMI cartridge optimized for AR-platform rifles*. The new 6mm ARC is basically a 6.5 Grendel necked down to 6mm, with the shoulder moved back around .030″. That pushed-back shoulder does reduce case capacity (and velocity), but we assume Hornady did that to create a shorter, proprietary chamber so people could not simply neck-down Lapua 6.5 Grendel brass, as has been done for years with Robert Whitley’s outstanding 6mm AR wildcat.
What Is the 6mm ARC Cartridge? The 6mm ARC cartridge is a new SAAMI-spec cartridge based on the 6.5 Grendel case necked down for 6mm bullets, with the shoulder moved back 0.030. Yes it is designed to run in AR15-platform rifles. You’ll need a new barrel, bolt, and mags. If you already have an AR chambered in 6.5 Grendel, the ONLY thing you need to change is the barrel. Everything else — bolt, magazines, gas system – is compatible with 6mm ARC.
▶ Official SAAMI Cartridge (not wildcat)
▶ Fits standard AR15-platform rifles
▶ Fits Short/Mini action bolt rifles
▶ Efficient short, fat case design
▶ 30-degree case shoulder
What Do I Need To Shoot the 6mm ARC?
Faxon and Ballistic Advantage are already producing barrels, with more manufacturers sure to follow. All the other required components are already on the market for 6.5 Grendel rifles. Aero Precision already offers complete 6mm ARC uppers.
If you’re converting a standard 5.56×45 mm (.223 Rem) AR15 upper to shoot 6mm ARC, you’ll need a 6mm barrel, a Type II 6.5 Grendel bolt carrier group, and new magazines. Some folks have suggested standard AR mags will work, but trust us, you want the magazines that have been designed for 6.5 Grendel. All the hardware you need is currently available at Brownells.
* While 6-6.5 Grendel shooters are known to run stout pressures, the new 6mm ARC cartridge has a relatively moderate Maximum Average Pressure (MAP) rating of 52,000 psi according to the official SAAMI specifications. For a variety of reasons, is wise to keep pressures in a semi-auto rifle moderate. Don’t chase the velocities you might get in a bolt-action gun.
Whidden Gunworks makes great sizing and seating dies. The Whidden full-length sizing die with neck bushing is very popular because it allows you to “tune” the neck tension by using different bushings, with larger or smaller inside diameters. In this video, John Whidden explains how to choose a the right bushing size for use with your neck-sizing and full-length sizing bushing dies.
For most applications, John suggest starting with the caliper-measured outside diameter of a loaded cartridge (with your choice of bullet), and then SUBTRACT about three thousandths. For example, if your loaded round mics at .333, then you would want to start with a 0.330 neck bushing. John notes, however, that you may want to experiment with bushings, going down a thousandth and up a thousandth. With thin In addition, as your brass ages and the necks harden, you may want to change your bushing size.
Quick Tip: Try Flipping Your Bushings
You may also want to experiment with “flipping” your neck bushings to alternate the side that first contacts the neck of the case. (One side of the bushing is usually marked with the size, while the other side is unmarked.) So try “number side up” as well as “number side down”.
Some folks believe that one side of the bushing may allow a smoother entry, and that this can enhance concentricity. Other people think they can get very slightly more or less neck tension depending on how the bushing is oriented. This is a subtle effect, but it costs nothing to experiment.
If one bushing orientation proves better you can mark the “up” side with nail polish so that you can always orient the bushing optimally. NOTE: We have confirmed that some bushings are actually made with a slight taper. In addition, bushings may get distorted slightly when the brand name and size is stamped. Therefore there IS a reason to try both orientations.
Do you have a concealed carry permit, or do you plan to carry a concealed handgun in the future? Then you can benefit from Beretta’s FREE 15-page e-book, Ten Essential Tips for CCW Holders. This eBook, in handy PDF format, helps gun owners select an appropriate handgun (and holster), understand legal obligations and responsibilities, and train effectively with the firearm. This short eBook offers many useful tips to consider, in particular for gun owners who are contemplating the pros and cons of everyday carry for themselves.
As the Beretta CCW booklet says, “Carrying a concealed handgun requires a certain amount of confidence. You need to be confident in your knowledge of laws and regulations. You have to have confidence in your accuracy, and you need to trust that you can carry a gun effectively, securely and comfortably. If a gun is a burden for you to carry, you probably won’t.”
Surprising Facts About Actual Defensive Handgun Use
You may be surprised to learn when and how handguns are actually used for self-defense. Most defensive uses are at very short range and the incident only lasts a matter of seconds. You need to be prepared, and train to be proficient drawing and aiming your weapon. And remember, shooting is a last resort, when a safe retreat is not available.
55% of gunfights take place in 0-5 feet.
20% of gunfights take place in 5-10 feet.
20% of gunfights take place in 10-21 feet.
95% of gunfights take place in 0-21 feet. (Source: FBI)
The average man can cover 21 feet of ground in 1.5 seconds.
The average gunfight is over in 3-5 seconds.
3 to 4 shots are usually fired.
Most gunfights take place in low-light conditions.
On average, one shot in four strikes someone.
Here are two (2) sample pages from Beretta’s CCW eBook.
Here’s a really great video about firearms crafting produced by Beretta, a legendary Italian gun-maker founded in 1526 — nearly 500 years ago. This movie, entitled “Human Technology”, is one of most impressive videos we’ve ever featured on this site. It’s that good. You’ll see an amazing blend of modern technology along with old-world artisanship — “a mesmerizing meld of the high-tech and the traditional”. (Daniel Xu, Outdoor Hub.)
“Human Technology is a singular and symbolic movie, its cast entirely made up of Beretta workmen, thus illustrating the perfect synthesis between craftsmanship and technology,” Beretta writes. This artistic movie by Ancarani Studio illustrates all the aspects of the manufacturing of a high-end Beretta shotgun. This video is a study in contrast. The movements of robotic assembly machines are juxtaposed with the centuries-old craftsmanship of stock carvers. Beautifully filmed and edited, this video should amaze and entertain anyone who loves fine firearms. (Full-screen HD Recommended.)
Tactical competitor Zak Smith stores his elevation and wind drift data on a handy laminated data card. To make one, first generate a come-up table, using one of the free online ballistics programs such as JBM Ballistics. You can also put the info in an Excel spreadsheet or MS Word table and print it out.
Above is a sample of a data card. For each distance, the card includes drop in inches, drop in MOA, drop in Mils. It also shows drift for a 10-mph cross wind, expressed in inches, MOA, and mils. Zak explained that “to save space… I printed data every 50 yards. For an actual data-card, I recommend printing data every 20 or 25 yards.” But Zak also advised that you’ll want to customize the card format to keep things simple: “The sample card has multiple sets of data to be more universal. But if you make your own data card, you can reduce the chance of a mistake by keeping it simple.”
Once you have the card you can fold it in half and then have it laminated at a local office store or Kinko’s. Keep this in your pocket, tape it to your stock, or tie the laminated card to your rifle. If you regularly shoot at both low and high elevations, you may want to create multiple cards (since your ballistics change with altitude). To learn more about ballistic tables and data cards, check out the excellent “Practical Long-Range Rifle Shooting–Part 1″ article on Zak’s website.
Scope-Cover Mounted Ballistics Table
Another option is to place your ballistics card on the back of the front flip-up scope cover. This set-up is used by Forum member Greg C. (aka “Rem40X”). With your ‘come-up’ table on the flip-up cover you can check your windage and elevation drops easily without having to move out of shooting position.
Greg tells us: “Placing my trajectory table on the front scope cover has worked well for me for a couple of years and thought I’d share. It’s in plain view and not under my armpit. And the table is far enough away that my aging eyes can read it easily. To apply, just use clear tape on the front objective cover.”
Today, June 21, 2022, is Summer Solstice! This means today has the longest period of daylight of any day of the year. And July is right around the corner. That means “peak heat” summer conditions. It’s vitally important to keep your ammo at “normal” temps during the hot summer months. Even if you use “temp-insensitive” powders, studies suggest that pressures can still rise dramatically when the entire cartridge gets hot, possibly because of primer heating. It’s smart to keep your loaded ammo in an insulated storage unit, possibly with a Blue Ice Cool Pak if you expect it to get quite hot. Don’t leave your ammo in the car or truck — temps can exceed 140° in a vehicle parked in the sun.
To learn more about how ambient temperature (and primer choice) affect pressures (and hence velocities) you should read the article Pressure Factors: How Temperature, Powder, and Primer Affect Pressure by Denton Bramwell. In that article, the author uses a pressure trace instrument to analyze how temperature affects ammo performance. Bramwell’s tests yielded some fascinating results.
For example, barrel temperature was a key factor: “Both barrel temperature and powder temperature are important variables, and they are not the same variable. If you fail to take barrel temperature into account while doing pressure testing, your test results will be very significantly affected. The effect of barrel temperature is around 204 PSI per F° for the Varget load. If you’re not controlling barrel temperature, you about as well might not bother controlling powder temperature, either. In the cases investigated, barrel temperature is a much stronger variable than powder temperature.”
This Editor had the personal experience of 6mmBR hand-loaded ammo that was allowed to sit in the hot sun for 45 minutes while steel targets were reset. The brass became quite warm to the touch, meaning the casings were well over 120° on the outside. When I then shot this ammo, the bullets impacted well high at 600 yards (compared to earlier in the day). Using a Magnetospeed, I then chron-tested the sun-heated ammo. The hot ammo’s velocity FPS had increased very significantly — all because I had left the ammo out in the hot sun uncovered for 3/4 of an hour.
LESSON: Keep your ammo cool! Keep loaded ammo in the shade, preferably under cover or in an insulated container. You can use a SEALED cool pack inside the container, but we do NOT recommend H20 ice packs. And don’t have the container do double duty for food and beverages.
Powder Heat Sensitivity Comparison Test
Our friend Cal Zant of the Precision Rifle Blog has published a fascinating comparison test of four powders: Hodgdon H4350, Hodgdon Varget, IMR 4451, and IMR 4166. The first two are Hodgdon Extreme powders, while the latter two are part of IMR’s Enduron line of propellants.
The testers measured the velocity of the powders over a wide temperature range, from 25° F to 140° F. Hodgdon H4350 proved to be the most temp stable of the four powders tested. [NOTE: New Alliant Reloder TS 15.5 has also proved very temp stable in AccurateShooter’s range tests.]
Do you know how gun primers are made — how the explosive elements are applied into those tiny cups? Find out by watching this video filmed at a Federal ammunition factory. It starts out with empty primer cups loaded, 1000 at a time, into trays using vibration (0:05 time-mark). While much of the process is automated, there is still a significant role played by production workers who apply a green, paste-like charging compound to the inside of hundreds of primer cups.
At the 0:17-second time-mark you can see the factory worker “charging” the primers with the priming compound. After the cups are filled, then the plate of cups “mates up with a plate of anvils” (0:40 time-mark). Then the primers are unloaded from trays and inspected.
Primer “Mysteries and Misconceptions” Article
There is an excellent article about primers on the Shooting Times website. This authoritative Shooting Times article explains the fine points of primer design and construction. The author reveals some little-known facts about primers and corrects common misconceptions. Here are some highlights:
Size Matters
Useful Trivia — even though Small Rifle and Small Pistol primer pockets share the same depth specification, Large Rifle and Large Pistol primers do not. The standard pocket for a Large Pistol primer is somewhat shallower than its Large Rifle counterpart, specifically, 0.008 to 0.009 inch less.
Magnum Primers
There are two ways to make a Magnum primer — either use more of the standard chemical mix to provide a longer-burning flame or change the mix to one with more aggressive burn characteristics. Prior to 1989, CCI used the first option in Magnum Rifle primers. After that, we switched to a mix optimized for spherical propellants that produced a 24% increase in flame temperature and a 16% boost in gas volume.
Foiled Again
Most component primers have a little disk of paper between the anvil and the priming mix. It is called “foil paper” not because it’s made of foil but because it replaces the true metal foil used to seal early percussion caps. The reason this little disk exists is strictly a manufacturing convenience. Wet primer pellets are smaller than the inside diameter of the cup when inserted and must be compacted to achieve their proper diameter and height. Without the foil paper, the wet mix would stick to the compaction pins and jam up the assembly process.
We have used NO-LEAD Cleaner in rimfire benchrest rifles similar to this modified Suhl 150-1. It helped restore accuracy with minimal brushing.
Made by the same smart folks that created Wipe-Out™, and Carb-Out™, NO-LEAD Brushless Lead Remover™ really works. Honest. If you are an active rimfire shooter, or if you shoot cast lead-alloy bullets in centerfire rifles and pistols, you should try this product. We now use NO-LEAD in our rimfire benchrest rifles, and in some centerfire guns that receive a steady diet of soft-alloy cast bullets (90%+ lead). (With rimfire guns, you don’t need to use NO-LEAD very often — maybe every 300-400 rounds unless you have a real fouler of a barrel.)
If you’ve got stubborn lead fouling in a rimfire barrel, or on a pistol’s muzzle brake/compensator, you should definitely give this stuff a try. We don’t know how but it does soften lead deposits. The manufacturer says you don’t need brushes, but we found that a bit of brushing (after NO-LEAD application) can help remove more serious lead build-up.
Yes we were surprised to find a lead remover that really works. We tried a half-dozen other lead “cleaners” that promised to dissolve lead and most of them, we discovered, are nearly useless. There’s a reason for that, as the lead alloys used in bullets don’t react to typical petrochemical-based solvents. It took the Wipe-Out chemists over five years to perfect this water-based solution that really does dissolve lead.
NO-LEAD Cleaning Procedure — Read Carefully NO-LEAD Lead Remover is a clear, red gel that is easy to apply. Just swab it in your bore (or on muzzle brakes) with wet patches or bore mop and let it sit for a few minutes. (The manufacturer says you can leave the NO-LEAD for up to 20 minutes, but that long of a dwell time does not seem necessary with our rimfire barrels.) When it contacts lead it will start to foam and you’ll see that the NO-LEAD solvent turns a pastel pink when it dissolves lead. The pink comes from the formation of lead oxide. After the recommended dwell time, simply patch out the dissolved lead deposits (you can also use a nylon brush for stubborn lead build-up).
NOTE: After cleaning, it is very important that you get all the NO-LEAD out of your barrel, and neutralize it. We recommend following the application of NO-Lead with Wipe-out or Patch-Out to neutralize the NO-LEAD, clear the bore, and remove residual carbon and copper fouling. If you don’t have Wipe-Out or Patch-out, flush the barrel thoroughly with Rubbing Alcohol or even a solution of Dawn dish detergent — then re-oil the bore.
Be Sure to Neutralize NO-LEAD After Use
Remember that N0-LEAD is a strong, slightly acidic chemical that needs to be neutralized after use. If you leave it on a nice, blued barrel for too long, it can harm the bluing. NO-LEAD will remove all the surface oils from the barrel bore. For this reason it is recommended that you neutralize NO-LEAD with Wipe-Out, or Patch-Out, which both contain effective corrosion inhibitors. If you don’t have those products, once you’ve flushed the NO-LEAD with something like rubbing alcohol, then follow with a gun oil. Caution: A petroleum-based gun oil will NOT, by itself, neutralize NO-LEAD. You need to neutralize first, then apply the corrosion inhibitor (or do it all in one step with Wipe-Out or Patch-Out).
Where to Buy NO-LEAD Lead Remover
NO-LEAD Lead Remover costs $19.50 for an 8 oz. squeeze bottle with a flip-top spout. This product is sold directly by Sharp Shoot-R Precision Products through Sharpshootr.com, or you can purchase NO-LEAD through many other online vendors. For more information, send an email via the Sharp Shoot-R Contact Form or or contact SharpShoot-R at (785) 883-4444. You can ask for Terry Paul, Sharp Shoot-R’s owner and the master chemist who developed the NO-LEAD formula.
Vertical stringing is a common problem that all precision shooters will face sooner or later. In addition to ammo inconsistencies, many other factors can cause vertical stringing. Accordingly, it’s important that you analyze your gun handling and bench set-up systematically.
EDITOR: Folks, READ THIS ARTICLE! You WILL benefit. There are some VERY important insights here. You’ll learn ways to set up your gun better, and check for various technical issues. That can save you time at the range and save you money spent on expensive bullets and powder.
In this article, Hall of Fame benchrest Shooter Speedy Gonzalez explains how to eliminate mechanical and gun-handling problems that cause vertical spread in your groups. Speedy’s article addresses the many human and the hardware factors that can cause vertical.
Speedy Gonzalez, noted shooter, gunsmith and member of the Benchrest Hall of Fame, offers these pearls of wisdom to help you eliminate vertical in your shot strings. Remember that vertical can result from myriad gear issues and gun-handling mistakes. Try to isolate one item at a time as you work to improve your groups.
BAGS and REST–VERY IMPORTANT
• Front Rest Wobble — You will get vertical if the top section of the front rest is loose. Unfortunately, a lot of rests have movement even when you tighten them as much as you can. This can cause unexplained shots.
• Rifle Angle — If the gun is not level, but rather angles down at muzzle end, the rifle will recoil up at butt-end, causing vertical. You may need to try different rear bags to get the set-up right.
• Front Bag Tension–Vertical can happen if the front sand bag grips the fore-arm too tightly. If, when you pull the rifle back by hand, the fore-arm feels like it is stuck in the bag, then the front bag’s grip is too tight. Your rifle should move in evenly and smoothly in the sand bags, not jerk or chatter when you pull the gun back by hand.
• Sandbag Fill — A front sandbag that is too hard can induce vertical. Personally, I’ve have never had a rifle that will shoot consistently with a rock-hard front sandbag. It always causes vertical or other unexplained shots.
• Bag Ears — If the channel between the Rear Bag’s ears is not in line with the barrel, but is twisted left or right, this can affect recoil and vertical consistency. And take note — if the bag is off-axis quite a bit, you can also get horizontal stringing.
• Reliability — ALL your bench equipment must work flawlessly. If it doesn’t, get it fixed or get rid of it. We need all our attention on wind flags.
GUN HANDLING and BENCH TECHNIQUE
• Be Consistent — You can get vertical if your bench technique is not the same every shot. One common problem is putting your shoulder against the stock for one shot and not the next.
• Free Recoil — Free recoil shooters should be sure their rifle hits their shoulder squarely on recoil, not on the edge of their shoulder or the side of their arm.
• Head Position — Learn to keep your head down and follow-through after each shot. Stay relaxed and hold your position after breaking the shot.
• Eyes — Learn to shoot with both eyes open so you can see more of the conditions.
• Last Shot Laziness — If the 5th shot is a regular problem, you may be guilty of what I call “wishing the last shot in”. This is a very common mistake. We just aim, pull the trigger, and do not worry about the wind flags. Note that in the photo above, the 5th shot was the highest in the group–probably because of fatigue or lack of concentration.
• Last Shot Low — I hear a lot of discussion about low shots in a group and apparently this occurs a lot on the 5th shot. If your 5th shot that goes out most of the time, you can bet you are doing something at the bench.
• Seating — When possible, bring your own stool so that you can sit comfortably, at a consistent height, every time you shoot.
LOAD TUNING
• Find the Sweet Spot — A load that is too light or too heavy can cause vertical problems. When you’ve tuned the load right, you should see a reduction in vertical. Even 0.1 grain may make a difference, as will small changes in seating depth.
• Primers — If you’re getting vertical, and everything else looks fine, try another brand of primers. And remove the carbon from the primer pockets so the primers seat uniformly every time.
• Case Prep — When you chamfer the inside of your case necks make sure they are smooth enough that they don’t peel jacket material off when you seat the bullet. Bullets with J4 Jackets (like Bergers) and Lapua Scenar bullets seem more prone to jacket scratching or tearing than Sierra bullets.
• Shell Holders — Keep shell holders clean, in both your press and priming tool. I have seen so much dirt/crud in shell holders that the cases end up get sized crooked because the rim is not square to the die.
• Water in Cases — I see people walking around with case necks turned up in the loading block. A lot of the time there is condensation dropping from the roof of your loading area. If one drop of water gets in a case you are in trouble. How many times have you had a bad low shot when it has been raining and you have been walking around with your cases turned up in your block?
MECHANICAL and HARDWARE ISSUES
• Barrel Weight — A lot of rifles are muzzle-heavy. Some rifles have too heavy a barrel and this causes vertical, especially when shooting free recoil. Basically the gun wants to tip forward. The remedy is to trim or flute the barrel, or add weight in the rear (if you can stay within weight limits).
• Unbalanced Rifle — If the rifle is not balanced, it does not recoil straight, and it will jump in the bags. If the rifle is built properly this will not happen. Clay Spencer calls this “recoil balancing”, and he uses dual scales (front and rear) to ensure the rifle recoils properly.
• Firing Pin — A number of firing-pin issues can cause vertical. First, a firing pin spring that is either too weak or too strong will induce vertical problems. If you think this is the problem change springs and see what happens. Second, a firing pin that is not seated correctly in the bolt (in the cocked position) will cause poor ignition. Take the bolt out of rifle and look in the firing pin hole. If you cannot see the entire end of firing pin it has come out of the hole. Lastly, a firing pin dragging in bolt or shroud can cause vertical. Listen to the sound when you dry fire. If you don’t hear the same sound each shot, something is wrong.
• Trigger — A trigger sear with excessive spring load can cause problems. To diagnose, with an UNLOADED gun, hold the trigger in firing position and push down on sear with your thumb. If it is hard to push down, this will cause vertical problems.
• Stock Flex — Some stocks are very flexible. This can cause vertical. There are ways to stiffen stocks, but sometimes replacement is the best answer.
SCOPE ISSUES
• Lock Rings — This year alone I have seen nine lock rings on scopes that are not tight. Guess what that does to your group? Make sure yours are tight.
• Big Tubes Need Tension — We’ve observed that some 30mm scope rings are not getting tight enough, and scopes are slipping in the rings under recoil. This will cause point of aim movement.
• Windage Bases — If you’re using a conventional-style single dovetail with rear windage adjustment, make sure both sides of the windage screws are tight. This can induce both windage AND vertical issues since the rear ring is held down by the windage tension.
AWARENESS of CONDITIONS and READING WIND
• Basic Wind-Reading Rule–If you do not know how to read wind flags or are very inexperienced, try to shoot your group with the flags all going in one direction.
• Rate of Fire — The longer you wait between shots when a condition is changing, the more the condition change will affect your shots.
• Look Far and Wide — Learn to look at the whole field of flags, not just the row in front of you. Many times a change quite a ways out will cause shot to go out of your group well before that change shows up in front of your bench.
• Don’t Fear the Wind — When you realize that the wind is your friend you will become a much better benchrest shooter. By this I mean that wind skills can separate you from other shooters who have equally good equipment. To learn how to read the wind, you must practice in challenging winds, not only in good conditions.
• Watch Wind Direction AND Velocity — Pay attention to angle changes on flags. Even though you see the same windspeed indicators, angle changes make a big difference in your groups.
• Watch While You Wait — Between courses of fire, whenever possible, watch conditions on the range. That way you will be aware of any changes in conditions since your last group and you will be mentally prepared for the new condition.
SPECIAL ADVICE for HUNTING RIFLES
• Clean That Barrel — Most hunting rifle barrels do not get cleaned enough. If you keep barrel clean it will shoot better for you. You should clean your barrel well after every 10 to 12 shots. If you’re lazy, just use Wipe-Out.
• First Shot Inconsistency — Most hunting rifles will not put the first shot (after cleaning) with the subsequent shots. So, after cleaning, if you have a rifle that tosses that first shot high or wide, then shoot one fouling shot before going hunting or before you shoot for group.
• Barrel Heat — Thin-contour “sporter” barrels WILL change point of impact as they heat up. When testing loads for your hunting rifle, take your time and don’t let the barrel get hot on you.
Want to see a bullet hit a target in ultra-ultra-slow motion? Watch this video to witness some amazing things — such as a bullet jacket peeling back like a banana-skin (at time-mark 7:30). Some years ago, Werner Mehl of Kurzzeit.com produced a 10-minute video for the SHOT Show. This video has has been watched over 15 million times on YouTube, making it one of the most popular shooting-related videos in history. Employing cameras recording at up to 1,000,000 (one million) frames per second, Mehl’s bullet flight video has been called “astounding” and “mesmerizing”. If you haven’t seen it yet, sit back and enjoy!
Watch This Video! It’s Really Something Special…
LINK: Kurzzeit.com Video System
Click the link above to learn more about Werner Mehl and his super-sophisticated camera systems that can record at 1,000,000 frames per second. On the same linked page you can learn about the advanced chronographs designed by Werner. Werner has now retired from business, but he was a brilliant engineer and his high-speed cameras were truly amazing. CLICK HERE to see more high-speed bullet videos.
The 6mm ARC cartridge is a new SAAMI-spec cartridge based on the 6.5 Grendel case necked down for 6mm bullets, with the shoulder moved back 0.030. Yes it is designed to run in AR15-platform rifles. You’ll need a new barrel, bolt, and mags. If you already have an AR chambered in 6.5 Grendel, the ONLY thing you need to change is the barrel. Everything else — bolt, magazines, gas system – is compatible with 6mm ARC. 
Quick Tip: Try Flipping Your Bushings
Scope-Cover Mounted Ballistics Table
To learn more about how ambient temperature (and primer choice) affect pressures (and hence velocities) you should read the article 
Made by the same smart folks that created Wipe-Out™, and Carb-Out™, 
Where to Buy NO-LEAD Lead Remover
In this article, Hall of Fame benchrest Shooter Speedy Gonzalez explains how to eliminate mechanical and gun-handling problems that cause vertical spread in your groups. Speedy’s article addresses the many human and the hardware factors that can cause vertical. 
• Front Bag Tension–Vertical can happen if the front sand bag grips the fore-arm too tightly. If, when you pull the rifle back by hand, the fore-arm feels like it is stuck in the bag, then the front bag’s grip is too tight. Your rifle should move in evenly and smoothly in the sand bags, not jerk or chatter when you pull the gun back by hand.
