The Accurate, Long Range 6mm BR
© Glenn Burroughs
Some years ago there was a company that developed a nearly perfect cartridge. And although it was intended for distances of less than five hundred yards, with the proper barrel twist and a heavier bullet it was very accurate to one thousand yards. Not only was it accurate over a variety of distances, but it did not use much powder, had little recoil, was easy on barrels, and was downright attractive.
Glenn with his original 6mm BR rifle (1.520" case length) built by Clay Spencer of Scottsville, VA.
For some reason there was no fanfare given this cartridge. One rifle was offered but was only available by special order. It didn’t help its popularity that no factory ammo was available when it was first announced. The little cartridge was not the most popular kid on the block and was almost forgotten.
Some years later another company, searching for a cartridge that would compete with the 308 Winchester in 300 meter competition, realized that this little cartridge had great long range possibilities. Once they decided it was just what they were looking for they changed only the chambering specifications to handle heavier bullets, and they named it the 6mm Norma BR.
Of course anyone with an interest in accurate rifles would have guessed this little mystery cartridge was the 6mm Norma BR. It was Norma that gave rebirth and a good life to the 6mm Bench Rest Remington design. In the mid-1990s Norma wanted to develop a 300-meter cartridge that was more accurate and had less recoil than the 308 Winchester. Using a heavy 6mm bullet, they experimented with two cases, the 6PPC and the 6mm BR Remington. The 6PPC was dropped because of its odd head size and limited powder capacity for heavy bullets.
Norma, recognizing the long range capability of the 6mm BR Remington, modified the chamber specifications to allow for longer bullets; the throat angle was changed to 1.5 degree instead of 3 degrees, and the twist was changed to stabilize the heavy bullets. Changing the chamber specifications required that they give the cartridge a new name, and they chose to call it the 6mm Norma BR.
According to Norma the barrel life of a 6mm Norma BR is about twice that of a 243 Winchester, somewhere over four thousand rounds. When comparing the 6mm Norma BR to a 308 Winchester loaded with a 168 grain bullet, the 6mm BR has much less recoil and wind drift is improved by at least twenty percent.
Accuracy is about the same, assuming the wind is calm or you are perfect at reading wind flags. Norma is proud to note that since its introduction the 6mm Norma BR has been a favorite with international 300 meter shooters and almost every existing world record today has been set with this cartridge. It has also proven a good choice for long range shooting and has been used to shoot ten-shot groups under four inches at 1000 yards.
Original 6mm BR box on the bottom, middle are unprimed cases for the 6mm BR Remington and the top is 6mm BR Remington rounds factory loaded with 100 grain bullets.
Several manufacturers have been savvy enough to offer rifles chambered in 6mm Norma BR. Savage in particular has recognized the capability of the cartridge and chambers at least three highly accurate rifles for it; the 12 Series Varmint, the Model 12 F-Class, and the Model 12 Benchrest Dual Port. From what I can determine these rifles are winning most of the matches where factory rifles are entered. And Cooper Firearms of Montana offers the chambering in their Model 22. I suspect there are more. Oddly enough, just a few years ago you could still get a 6mm Bench Rest Remington with a 1:14-inch twist barrel in the Model 40-XBBR™ KS through the Remington Custom Shop.
There is considerable controversy about the case design of the 6mm Norma BR. The case is identical to the 6mm BR Remington but many argue that Norma started with the Remington case, and then modified it to create their long range wonder. An excursion on the internet will provide numerous instances where it is emphatically stated that Norma did change the 6mm Bench Rest Remington case.
A typical example reads, “Norma standardized their set of chambering specifications for a very low drag (VLD) bullet of over 100 grains, thus realizing the long-range capabilities of the cartridge. This resulted in a much longer neck on the Norma cartridge.” A much longer neck? Well, they did change the chambering specifications, but they did not change the neck dimensions.
Perhaps one contributor to the confusion has to do with reamer specifications… and there are certainly many different versions of reamers for the 6mm BR. Besides using the standard SAAMI specs, reamer specifications are also created based on the desires and whims of the gunsmith, or the customer, or from measurements from the brass that will be used. But with all of this variation there is still only one version of loading dies available for the 6mm BR, and until recently they were usually labeled “6mm BR Remington”. The sizing dies for both cartridges are identical.
To get to the gist of the matter I contacted Redding and asked about the differences between the 6mm Norma BR and 6mm Bench Rest Remington cartridges. Redding stated, “Reloading dies designed for either cartridge will be exactly the same. The confusion comes from the fact that Remington tends to make their cases near the midpoint of the .008" diameter tolerance and Norma tends to make their cases near the maximum.
Years ago, gunsmiths used to tighten up the chamber dimensions to better fit the Remington cases. This was before Lapua and Norma cases were available. Lapua and Norma cases fit SAAMI/CIP spec chambers very well and there is no need to alter the dimensions of chambers to fit the cases tighter.” That response made it very clear that the two cartridges are the same… but there is more.
The ‘icing on the cake’ is provided by a statement Lapua makes about their 6mm Norma BR brass. This information can be found on the MidwayUSA website where the Lapua 6mm Norma BR brass is described. Clearly stated under a Lapua logo is the declaration; “Brass is headstamped 6MM Norma BR to meet European CIP requirements but the case dimensions are IDENTICAL to the 6mm BR Remington. This may cause confusion as some people understand the cartridge cases are different in dimensions. In fact it is the chamber dimensions, not the cartridge dimensions that changed.
In 1995 Norma adopted the 6mm BR and submitted a new "chamber" specification for certification by the European CIP board. The chamber specification differs from the North American SAAMI specifications in the throat dimension. This change in the chamber throat dimension does not affect or change the cartridge case dimensions in any way.” Lapua makes it very clear that the two cartridge cases are identical.
What about the 6mm Bench Rest Remington, the cartridge used to create the highly successful 6mm Norma BR? This innovative cartridge was introduced by Remington in 1978, chambered in their 40X target rifle, and could be acquired only through the custom shop. Several variations of the 6mm BR had been around since the mid-1970s, so to prevent the new cartridge from being chambered in one of the older wildcat chambers the neck was lengthened by .040" for an overall case length of 1.560". Somewhere along the way the cartridge was also offered in the XP-100, a bolt action pistol that was chambered for cartridges from the 221 Fireball up to the 35 Remington. Like the 40X target rifle, the XP-100 was only available through the custom shop.
Original 6mm BR case on left and a 6mm Norma BR case on right. The .040" neck length difference is barely noticeable.
When Remington first offered the 6mm BR Remington factory ammo was not available and reloaders had to form their own cases. Most used a special brass offered in the mid-1970s by Remington called “URBR” (which I think stood for something like “universal Remington bench rest”). This 308 brass had two notable features; it had a small rifle primer pocket and had comparatively thin walls and included annealing to facilitate case forming.
At some later point Remington offered 6mm BR factory loaded ammunition. Interestingly, at least some of Remington’s ammo was loaded with 100 grain bullets (see photo). If that ammo was available today it might shoot well in a rifle chambered for the 6mm Norma BR. But without the availability of a factory rifle the 6mm Bench Rest Remington never really had a chance at success. Although Remington had developed what has turned out to be one of the most accurate cartridges ever, they never released it to the general public by making it a standard factory offering.
Then there is the cartridge that started it all… the 6mm BR. The early history of the 6mm BR is somewhat murky and the real story of its origin may never be known. Although it was never offered as a standard cartridge its name can be determined based on the statement Remington placed on the 6mm BR Remington cartridge boxes (see photo) which reads; “Notice: This 6mm BR Rem. Cartridge will not fit in 6mm BR chambers.”
The history of this cartridge is not well documented, and the opinions on how it originated are many. Sierra Bullets has a brief history of the cartridge in one of their loading manuals which reads; “In the late 1970s, Remington marketed a line of cases under a rather unique premise - the brass was not intended to be loaded as it came from the factory.
Known as the Remington Bench Rest case, this was a thin-walled 308 Winchester case dimensioned to accept the small rifle primer and specifically annealed for case forming. Behind the scenes, Remington’s Mike Walker and Jim Stekl had been working with a series of short, squat little cartridges based on the 308 head size. Based on their results from testing and actual benchrest competition, the BR family (as they came to be called) showed tremendous promise. Since then, both the 22 and 6mm BR chamberings have been offered in Remington’s vaunted 40-X target rifles.”
Of course there are other claims to be the source for this cartridge. Cartridges of the World, 9th Edition, includes this statement; “the 6mm BR Remington is one of eight cartridges based on the 308x1½-inch case”. The case referred to is commonly known as the 308x1.5 Barnes, and is basically a shortened 308 Winchester that was developed in 1961.
Since the 308x1.5 Barnes was one of many cases based on the 308 Winchester, and has a large primer pocket, it would not seem logical that this would have been used as the basis for the 6mm BR. Additionally, the 6mm BR was slightly longer than the 308x1.5 Barnes. But who knows? Maybe the 308x1.5 Barnes was the parent case. There are other claims of origination but I will leave those for the interested reader to investigate.
I suspect that Sierra’s short history of the 6mm BR is pretty close to how things came about. My guess is that Jim Stekl of Remington was probably the primary innovator for the cartridge. More than likely he used Remington’s “URBR” brass when he created his 22 BR in the mid-1970s. The specifications for his case were identical to the 6mm BR except for the 22-caliber neck diameter. Shooting the 22-caliber version of this cartridge, Jim won the 1975 match at the Pine Tree Club at Johnstown, New York with an aggregate of .1776".
My first experience with the 6mm BR was several years ago when I decided to have a rifle re-barreled and chambered for the 6mm Norma BR. I took the rifle to Clay Spencer of Scottsville, Virginia and told him of my plans, and he immediately asked why I did not want the original 6mm BR. Of course the main reason was that I had never heard of it. That’s when he gave me a brief history of the cartridge and spent a considerable amount of time trying to erase my confusion between the different 6mm BR’s.
Clay has been chambering rifles for the original 6mm BR since the 1980’s and even offers his “Virginia Hog Rifle” in this caliber. Since this rifle is guaranteed to shoot a quarter inch, five-shot group at 100 yards he only offers it chambered in cartridges that can meet the challenge. Each of these cartridges must be extremely accurate and the original 6mm BR qualifies. At Clay’s recommendation I decided to go with the 6mm BR chambering. Since my acquisition of that highly accurate rifle I have also owned a 6mm Norma BR. I would have to say that if I could only have one rifle, it would be a 6mm Norma BR.
So there you have it… all you need to know about the case differences and a little of the history. In a nutshell, there are three versions of what is commonly called the 6mm BR; the original and slightly shorter 6mm BR, the 6mm Bench Rest Remington, and the 6mm Norma BR. The case dimensions for all three cartridges are the same except for one dimension… the neck length of the original 6mm BR is .040" shorter than the other two cartridges.
We owe a debt to those creative individuals at Remington for the original design of the 6mm BR. And we have Norma to thank for recognizing the accuracy and long range capabilities of the 6mm BR Remington, and providing it to the shooting world as the 6mm Norma BR. If Norma had not stepped into the picture this amazing cartridge may have faded into oblivion. Last, but certainly not least, even Norma’s version of the cartridge might not have made it had it not been for Lapua. Once Lapua endorsed the 6mm Norma BR by including it in their respected line of match brass the cartridge was on its way to a bright future.
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Glenn Burroughs is a retired computer systems manager with a lifelong love of guns. His main areas of interest are accurate rifles, wildcat cartridges, reloading and bench shooting. He also enjoys an occasional trip out west to the prairie dog country. Glenn was a columnist for Precision Shooting magazine and also wrote articles for Varmint Hunter magazine. He resides in Lynchburg, Virginia.