Broadsword M89 18″ Rifle-6mm MAX

Why the 6MM MAX?

The 6mm MAX is pressure tested to SAAMI standards of 55k psi.  It is a brand new cartridge designed for the unmodified mil-spec .378 bolt face, and a full mass bolt carrier group.  The 6mm MAX holds 35 grains of water capacity which ultimately determines the energy potential of the cartridge.  In this case, 1750+Lbs of energy.  Why is that so significant?  The 6mm MAX can launch an 87 gr Berger VLD at 3009 fps from a 24″ barrel.  This produces 1749 lbs at the muzzle, 1504 lbs at 100 yards, 1093 lbs at 300 yards, 775 lbs at 500 yards, 533 lbs at 700 yards, and stays supersonic past 1000 yards.  These ballistics are at standard atmospheric pressure and temperature.

Cartridge designers have struggled with 2.26 OAL, and having enough room for increased case capacity.  Until recently, there hasn’t been a .378 case head cartridge available that has a 35 gr water capacity.  This amount of water capacity is the engine that can power heavier, and high ballistics coefficient bullets up to 100 grs.  The 6mm MAX can do this within the constraints of the AR-15, and function flawlessly.  So the end result is that the 6mm MAX can push bullets 55 gr to 100 gr, and do it with the same 2.30 OAL.  Some designs have emerged shorter and fatter to accommodate a bullet with better BC and enough powder for useful velocities.  When comparing the water capacity of 24 Nosler (29 grs), 6.8 SPC (35 grs), 5.56 x45 NATO (28.5 grs), 6×45 (29 grs), 6 ARC (34 grs), 6.5 Grendel (35 grs), .224 Valkyrie (34.5 grs), and what do we get?  For the cartridges with .378 case head, powder capacity is less than the 6mm MAX.  For the cartridges with larger case heads, you get the same amount of powder or less than the 6mm MAX.  The end result is that the 6mm MAX (35 grs) allows for a .378 mil-spec bolt face with full lug integrity and powder to push the heavies at useful velocities.

BC Precision Ballistics has spent 3 years and thousands of hours in research and range time to get the 6mm MAX perfected.  Our case is only slightly rebated for a well balanced cartridge maximizing capacity and 100% reliability.  We designed the chamber for functionality in a repeater and for accuracy.  Sometimes those two requirements conflict with each other as reliability requires loose tolerances, and accuracy requires tight tolerances.  We consulted with many lifelong industry experts throughout the chamber/reamer design and listened to what they had to say.  We utilize carbide reamers for our builds, and our tolerances are kept exact for predictable performance.

Wondering about accuracy?  On Aug 6^th, 2022, I competed with the 6mm MAX in F-Class with my local club the Central Texas Silhouette Association or CTSA.  Full disclosure on me?  I’m an old F-Open High Master.  My normal competition gun is a .243 30″ Bartlein barrel running 105 hybrids at 3050 fps with a stout load of H4831SC.  The 6mm MAX is not a competitive F-Open cartridge by any stretch of the imagination, but I wanted to see an actual real world test of accuracy in the hot south Texas switching winds at 500 yards.  I used a 24″ Bartlein barreled hunting rig.  This is the same bolt rifle pictured on this web site.  It has 2600 rounds of testing down range, and is till holding sub-MOA with a load of H4895 tested to SAAMI standards of 53,000 psi.  The load was 26.6 grs of H4895, and 90 gr Lapua Scenar-L at 2.30 OAL.  This load was straight from our loading chart on this web site.  After the 3^rd relay my score was 568-6X.  Nothing to write home about by F-Class standards, but in the world of hunting and rifle accuracy these rounds would have HARVESTED GAME.

Brian Cook