Exclusive Shootout: 6mm Creedmoor vs. the 6.5
September 19, 2017
When Hornady introduced the 6.5 Creedmoor about 10 years ago, competitive shooters took note of the fact that it duplicated the velocity of the earlier 6.5x47 Lapua. That cartridge and its 6x47 Lapua offspring had already become favorites among those who strive to squeeze a handful of bullets into the same hole at great distances. Interest in the 6.5x47 Lapua gave the fledgling 6.5 Creedmoor a running start toward success.
The 6.5 Creedmoor is the .30 TC case necked down to 6.5mm (0.264 inch) and the 30-degree shoulder pushed back 0.022 inch. Due to taper in the body of the case, pushing back the shoulder decreases diameter at the body/shoulder juncture by 0.002 inch. Otherwise, the two cases are identical, including a maximum length of 1.920 inches. Neck down the 6.5 Creedmoor case for 0.243-inch bullets and you have the 6mm Creedmoor. It began life several years ago as a wildcat and quickly began to rival its parent in popularity among log-distance competitors. Hornady introduced 6mm Creedmoor factory ammo loaded with match and hunting bullets in early 2017.
The Lapua cartridges are for handloaders only, but Hornady offers match-grade 6mm and 6.5 Creedmoor ammunition. Federal has 6.5 Creedmoor factory-loaded ammo, including the American Eagle 140-grain Match bullet. Winchester also offers several 6.5 Creedmoor loads, including a 140-grain match load. Nosler's Match Grade loading has that company's 140-grain Custom Competition bullet. And HSM has just announced two 6.5 Creedmoor factory loads with 140-grain Berger VLD Hunting and Sierra GameKing bullets.
Ruger was the first manufacturer to offer a factory rifle in 6.5 Creedmoor. Soon after the cartridge was introduced, I used a Hawkeye bolt-action rifle chambered for it to bag a very nice pronghorn antelope. I have mostly written about the 6.5 Creedmoor from a hunter's perspective, but this time I will don my competitive hat and take a close look at both Creedmoor cartridges in Ruger Precision Rifles. Prior to the introduction of the Precision Rifle, Ruger technicians tested a number of them and came up with an overall average accuracy of around 0.80 inch for five-shot groups at 100 yards with factory ammunition. That gave me an accuracy goal to shoot forâ€”and possibly beat.
I have shot so many different rifles through the decades that it takes something really special to get my attention. As much as I love walnut and blued steel, I appreciate accuracy in any form, and the Precision Rifle has my undivided attention. And while this report is primarily about cartridges and not rifles, I cannot resist mentioning a couple of items.
The fully adjustable Marksman triggers of the test rifles broke crisply at a consistent 35 and 37 ounces, with no trace of creep or overtravel. Close examination of the bores with a Lyman Digital Borecam revealed smooth 5R rifling. Attaching identical Bushnell Elite Tactical DMR II-i scopes with a magnification range of 3.5-21X to the rifles moved their weights close to 15 pounds, which made both quite comfortable to shoot.
A few challenges had to be met prior to shooting. To remove the bolt of the Precision Rifle, the rifle's hinged buttstock has to be swung to the side and remain there while the bore is being cleaned. A Gun Vise from MTM held the rifle firmly in position with its stock folded. A cleaning rod guide from Sinclair International kept bore solvent from dripping into the trigger mechanism and prevented unnecessary wear on the rifling at the chamber throat.
The AR-style handguard is fine when shooting prone with a sling or bipod, but it encourages canting when resting on a regular sandbag. There is no problem with canting so long as it remains precisely the same for each shot, but doing so consistently with regular bags is difficult. A Bulls Bag Shooting Rest from Brownells placed atop a Lyman height-adjustable Bag Jack proved to be the perfect solution. The toe of the stock rested firmly on a regular bunny bag.
Back to the two Creedmoor cartridges. SAAMI maximum overall length is 2.800 inches. Some factory ammunition exceeded that, but the Ruger magazine with an interior length of 2.840 inches was plenty roomy. When loading the rifle single- shot, as was done with some of my longer handloads, cartridge overall length can exceed magazine length, but if the magazine is to be used, 2.830 inches is about maximum for trouble-free feeding.
Seating bullets out to long overall cartridge lengths in factory ammo and in handloads leaves plenty of space inside cases for powder, and chamber throats in the Ruger rifles in both calibers are long enough to accommodate them. When checked with a Hornady Overall Length Gauge, the dimension from case head to the point on the ogive of a bullet that contacts the rifling was 2.160 inches for the rifle in 6mm Creedmoor and 2.225 inches for the 6.5 Creedmoor. The amount of bullet freetravel prior to rifling engagement for various factory loads and handloads is shown in the accompanying accuracy chart.
Preparing handloads for the two rifles, I used Hornady, Nosler, Starline, and Lapua cases. As this is written, only Hornady offers 6mm Creedmoor cases, so a Redding Series C die was used for necking down the others. The 6.5x47 Lapua case uses a Small Rifle primer, and it has a 1.5mm (0.059 inch) flash hole compared to the SAAMI minimum/ maximum of 0.074 to 0.078 inch for cases of American manufacture. It and its 6x47 offspring have been widely accepted by competitive shooters, so when Lapua began making the 6.5 Creedmoor case, it was given the same primer pocket and flash-hole diameters. Hornady and Nosler cases use Large Rifle primers and have flash holes of SAAMI-specified size. Starline offers cases pocketed for both primer sizes, and the cases have flash holes of standard size. The 0.058-inch decapping pins of Redding resizing dies work perfectly with both flash-hole diameters. The more standard 0.070-inch pin in other dies will have to be switched out before they are used to decap Lapua cases.
The same procedure was followed as I would if preparing for a match. When a cartridge is chambered, variation in case neck wall thickness (wall thicker on one side than the other) introduces misalignment between the axis of the bullet and the axes of the case and bore. A Hornady Neck Wall Thickness Gauge revealed as much as 0.007-inch variation in the four brands of cases. An electric screwdriver-powered Hornady Neck Turn Tool with its blade adjusted to shave brass only from the thick side of a case neck took care of that. Cases were then run through Redding Type S bushing-style neck-sizing dies with bushings 0.002 smaller than the neck diameter of a loaded round. When fired case fit became a bit too tight for easy bolt closure, a Redding body die was used to bump back shoulders. Bullets were seated with Redding Competition dies.
If perfectly concentric factory ammunition could be mass produced, few shooters could afford to buy it. My solution was to run each round of 6mm Creedmoor and 6.5 Creedmoor through the Hornady Concentricity Tool and mark the high side of the neck with a magic marker. As each round was placed into the magazine or manually chambered, its mark was oriented to the 12 o'clock position.
With the exception of the Sierra 110-grain MatchKing, overall lengths of 6mm Creedmoor handloads were compatible with the magazine. Due to the longer chamber throat of the rifle in 6.5 Creedmoor, several handloads exceeded magazine length. Best accuracy with the Sierra 130-grain Tipped MatchKing in the 6.5 Creedmoor was at a cartridge overall length of 2.840 inches, which put bullet noses against the front of the magazine. No feeding issues were experienced, but in a match shooting cartridges that rub against the front of the magazine would make me very uneasy. For best accuracy in the test rifle, cartridges loaded with the Nosler 140-grain RDF and Hornady 147-grain ELD Match were also too long for the magazine.Accuracy Results
During accuracy testing, I went with five shots per group. The barrel was completely cooled down between each four-group string by running water through the bore followed by four dry patches. I usually shoot one fouling shot prior to shooting the next group, and while that worked with the 6mm rifle, the 6.5mm required two fouling shots before settling down. Squeeze too much shooting into a single range session and group size becomes affected by shooter fatigue, so each session was limited to four hours.
Never in a thousand years will it happen again, but aggregate handload accuracy of the two rifles ended up exactly the same at 0.57 inch. Equally interesting is the fact that both rifles averaged less than half-MOA with five of the 12 handloads tried in each. Pure luck? Perhaps, but it might also serve as proof that Ruger has discovered a way to mass-produce consistency.
Because the 6.5 Creedmoor burns a smaller powder charge, match-level barrel accuracy life will be longer than with the larger 6.5-284 Norma. Recoil is also a bit lighter. And yet, as illustrated in the exterior ballistics comparison chart on page 30, when both cartridges are loaded to maximum velocities with the same bullet, there is not a great deal of difference in wind drift.
Reducing the neck diameter of a case decreases expansion ratio, and while barrel accuracy life with the 6mm Creedmoor will be less than for the 6.5 Creedmoor, I doubt if the difference is enough to be of concern to most competitors. On paper, the 6.5 Creedmoor slightly edges out its offspring at 500 and 1,000 yards, but a good shooter who knows how to read wind and mirage can dominate matches with either.
So which of the two cartridges is best? In long-range competition, shooter ability is far more important than slight differences in the performance of various cartridges. But even the best shooters are better able to take home gold when shooting cartridges that are easy on the shoulder. While both cartridges fit that description, the slightly lighter recoil of the 6mm Creedmoor places it a bit ahead in that department.
Those who might scoff at the idea of a mild-mannered 6mm cartridge becoming king of the hill in long-range competition should consider this: As this is written, a 2.6872-inch 10-shot group fired by Jim Richards is the smallest fired at 1,000 yards. His rifle was chambered for the little 6mm Dasher. It and the 6mm Creedmoor push long, high-BC bullets at about the same velocity, so they should be equally capable of winning matches.