Fortunately, while at USAMU, Cris Murray, one of the co-designers of the 6.8 mm SPC simultaneously developed an¯ assault rifle cartridge, with none of the platform imposed design compromises that limit both the 6.5 mm Grendel and 6.8 mm SPC. This an idealized¯ assault rifle cartridge, the 7 x 46 mm, offers better range and terminal performance than 6.5 mm Grendel, 6.8 mm SPC, or any other common assault rifle cartridges, including 5.45 x 39 mm, 5.56 x 45 mm and 7.62 x 39 mm. Since the 7 x 46 mm is based on the proven Czech military 7.62 x 45 mm cartridge, it has an established record feeding and functioning in both magazine and belt-fed full-auto fire. Likewise, recoil appears manageable and weapons remain controllable in FA fire, just as with the Czech cartridge. In addition, the 7 x 46 mm is optimized for shorter barrels and larger magazines than the heavier, bulkier, and harsher recoiling 7.62 x 51 mm/.308 cartridge. The 7 x 46 mm is truly the best assault rifle cartridge developed to date.
The main problem is that the 7 x 46 mm cartridge OAL is a bit too long to fit into the M4/M16 or other 5.56 mm size weapons/magazines, yet it does not need a receiver/magazine as large as those used by 7.62 x 51 mm/.308 platforms such as the M14, Mk11, M110.
As a result, the 7 x 46 mm requires new weapons--envision a rifle sized a bit larger than the AR15, but smaller than an AR10/SR25.
<Doc inserts ballistic gelatin shot using a 16 inch barrel, muzzle velocity of 2800 fps with a 120 grain bullert>
As you can see, 7 x 46 mm offers outstanding terminal performance very similar to 6.8 mm; 7x46 mm is just a bit better.
Both the 6.8 mm SPC and 7 x 46 mm were conceived and developed entirely by experienced end-users based on identified combat mission needs and end-user requirements as approved by their Commanders. Both the 6.8x43mm and 7x46mm were developed by the same design team at the same time. From day one everyone involved in this effort has acknowledged both cartridges, however, a decision was made to pursue deployment of 6.8mm initially, as it offered a more expeditious solution for improving current combat capability by simple, inexpensive modifications to existing weapons, while 7x46mm required new weapons platforms for optimal performance.
Again, bottom line:
-- 6.8 mm SPC is the best available solution to rapidly upgrade current 5.56 mm weapons.
-- If given a clean slate of paper and substantial development funds, the clear and obvious best cartridge for new design weapons is the 7 x 46 mm, as it offers greater soft tissue terminal performance, better intermediate barrier penetration, and greater maximum range and long distance performance than traditional assault rifle cartridges like the 5.45 x 39 mm, 5.56 mm, 7.62 x 39 mm, as well as the newer 6.5 mm Grendel and 6.8 mm SPC.
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