CARTRIDGE REVIEW – 6MM BR
6mm Norma BR is a standardised version of a wild cat that existed for some time.
Remington were the first to try and attempt to standardise this cartridge, but as they have done many times before and since, stuffed it up. Their specifications only allowed for relatively light projectiles such as the 70 grain Matchking, to be used with full efficiency, as they saw the BR as a purely bench rest case.
In 1996 Norma lengthened the throat to allow for the longer match projectiles, such as the 107 grain projectiles, to be seated out of the case for maximum case efficiency and better projectile/bore alignment. The 6mm BR Rem is all but dead now – nowadays if someone says 6mm BR they mean 6mm Norma BR.
The 308 x 1.5” Barnes was used as the parent case for many cartridges such as the 6mm Norma BR – the 6mm BR is basically a .243 Winchester with the case shortened to approximately 1.56” long. The BR cases also have provision for the use of a small rifle primer, rather than the large rifle primer used in cases such as the .243 Winchester. The small rifle primer provides sufficient ignition of the small powder column of the 6mm BR, and does it more consistently than a large rifle primer.
The 6mm BR is still a good bench rest calibre, but it really shines in long range competitions such as F Class, where it provides superior ballistics than the 223 or 308 Winchester. It also makes an excellent medium game cartridge where precision shots are required. The downside to the 6mm BR is that the short, fat cases do not like to feed out of a magazine, which isn’t important on any single shot target or varmint rifle.
Lapua manufacture unprimed brass and loaded ammunition for the 6mm BR. A box of 20 rounds loaded with 105 grain Scenar competition projectiles costs around $85. There are plenty of mediocre cartridges that you can buy for around 30% cheaper, but they won’t be a Lapua case with a Lapua competition projectile, so $85 is quite reasonable in my opinion.
Any rifle with a bold head size to suit the 308/243/22-250 family of cartridges can be re-barrelled for the 6mm BR, though as previously mentioned they may not feed out of the magazine. Because of the inherent accuracy of this cartridge it would be rare a follow-up shot would be required.
The 6mm Norma BR is a standardised cartridge, but there are many wildcats based off the 6mm BR which are quite popular within certain circles. The 6mm BRX is the BR case with the shoulder pushed forward for slightly more powder capacity – the 6mm Dasher pushes the shoulder further forward. Neck length is of little consideration to target shooters who feed each round into the gun singly, neither is the considerable time spend forming cases which will crack if not formed correctly. Anyone who knows me knows I hate ‘improved’ chambers – if you are chasing velocity just rechamber the rifle to .243 Winchester.