The Accurate, Long Range 6mm BR
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.
Home | Next Page>