07-21-2017, 05:17 PM
The wikipedia screenshot in post #34 is incorrect about 5.56x45 NATO being derived from .223 Remington. When .222 Special was given its military nomenclature of 5.56x45, it was not a NATO cartridge and did not receive NATO standardization until much later. .222 Special and 5.56x45 came well before .223 Remington nomenclature and production.
The specs for 5.56x45 brass are much different than .223 Rem SAAMI brass. Yield strength is substantially higher on the 5.56x45 brass, so that effects alloy and thickness, with thickness and reduced case capacity being the most measurable metrics for the layman.
As to the merits of the discussion about terminal performance, I'm of the opinion that even the .222 Remington was sufficient, and would have been a better case length to stick with, move the shoulder forward, and use a higher BC projectile with a longer ogive. Back then, even within engineering circles, muzzle velocity was the focus. There was one engineer within Army Ordnance who focused more on BC's function with regard to retained energy, and Stoner was aware of it too, evidenced by his suggestion of using a boat tail bullet to help meet the moving goal posts of the CONARC/Army Ordnance .30 cal nazis.
The Russians really got it right with the 5.45x39mm cartridge, using a short case that still allows 30rds to be carried in the same magazine profile as a 30rd AR15 mag, which also allows very high BC for caliber projectiles, unlike the 5.56x45. The Russians also used a lower working pressure so that weapon life is more manageable. That little 5.45x39 is a great cartridge as a result. A 5.56-6mmx39 based off that cartridge would have been about ideal for both common infantry and DMR loads, using a BC in the .450 G1 region and higher for the DM load.
![[Image: 5.56x45-vs-5.45x39.5.jpg]](https://www.ammoland.com/wp-content/uploads/2016/02/5.56x45-vs-5.45x39.5.jpg)
![[Image: 545ammo.jpg]](http://armslocker.com/pics/545ammo.jpg)
The specs for 5.56x45 brass are much different than .223 Rem SAAMI brass. Yield strength is substantially higher on the 5.56x45 brass, so that effects alloy and thickness, with thickness and reduced case capacity being the most measurable metrics for the layman.
As to the merits of the discussion about terminal performance, I'm of the opinion that even the .222 Remington was sufficient, and would have been a better case length to stick with, move the shoulder forward, and use a higher BC projectile with a longer ogive. Back then, even within engineering circles, muzzle velocity was the focus. There was one engineer within Army Ordnance who focused more on BC's function with regard to retained energy, and Stoner was aware of it too, evidenced by his suggestion of using a boat tail bullet to help meet the moving goal posts of the CONARC/Army Ordnance .30 cal nazis.
The Russians really got it right with the 5.45x39mm cartridge, using a short case that still allows 30rds to be carried in the same magazine profile as a 30rd AR15 mag, which also allows very high BC for caliber projectiles, unlike the 5.56x45. The Russians also used a lower working pressure so that weapon life is more manageable. That little 5.45x39 is a great cartridge as a result. A 5.56-6mmx39 based off that cartridge would have been about ideal for both common infantry and DMR loads, using a BC in the .450 G1 region and higher for the DM load.
NRA Basic, Pistol, Rifle, Shotgun, RSO
CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
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CCW, CQM, DM, Long Range Rifle Instructor
6.5 Grendel Reloading Handbooks & chamber brushes can be found here:
www.AR15buildbox.com