A lot of discussion these days is focused on the current "big 3" alternate calibers of the AR-15 platform: 6.8 SPC II, 6.5 Grendel, and 300 BLK. Each one offers various gains (or losses) when compared to the standard 5.56 NATO round used in our beloved rifles. At the same time, in other areas, the gun world is abuzz with talk about how the Army effectively shut down the individual carbine competition.

This got me thinking. Why not start a discussion about what exactly a new rifle should look like? I don't want to limit it just to the rifle, though, so let's discuss the cartridge as well. All of the stuff that we've been talking about as far as cartridge variations and rifle design has been limited by two factors:

- All of the new carbine/rifle designs are based around continued use
of 5.56 and STANAG magazines

- All alternate cartridges we talk about have been a compromise of capability and the ability to fit into the AR-15 platform

So let's discard those requirements for this discussion. If you read the original ORO reports about the .223 and the AR-15, it becomes apparent that the story of the Ar-15 is every bit as much about the evolution of the .223. This discussion should be no different.

So here are the ground rules:

1. We must determine an ideal cartridge for general infantry issue. You cannot use theoretical technology that doesn't exist yet or will be difficult to obtain in quantity. Bullets must conform to current laws of armed conflict.

2. We must "design" a rifle to use said cartridge and be the standard issue long arm to US forces

3. Costs should be kept reasonable, but not stingy. This is all an academic exercise and does not need to fit into any actual fiscal policy. But the end result should still be practical.

Some considerations based on past experiences:

The original ORO research that led to the M-16 determined that an average military firefight (up through WWII) occurred within 100 yards. Beyond that range, hit probability decreased dramatically. Beyond 300 yards, the chance of being struck by a bullet was essentially random. Beyond 300 yards, you were about as likely to be killed by a grenade or artillery as you were a rifle round. The .223 was developed to meet this spec, though the maximum range spec was extended to satisfy the Marine Corps. While the historical engagement distance is relatively close, experiences in Afghanistan have demonstrated a need to have consistent capability at longer ranges.

During testing of the .223 and the M-16, penetration and intermediate barrier was found to be a significant issue when compared to the 7.62x51. Not much has changed in that regard; and the desire for a better performing round like the 6.8 SPC and 6.5 Grendel illustrate the fact. Whatever cartridge we come up with should demonstrate range, accuracy, penetration, and good terminal ballistics.

Accuracy through repeated fire was important during the original ORO tests. Whatever configuration we choose should continue in this tradition, but realize that the ammunition/weapon combination contracted today is 2 MOA to 6 MOA, not exactly precision work. Sacrificing precision in order to gain something else is acceptable, though the choice is up to you.

Useful References

Hitchman, N. (1952). Operational Requirements for an Infantry Hand Weapon.
http://www.dtic.mil/cgi-bin/GetTRDoc...f&AD=AD0000346

Ehrhart, T. (2009). Increasing Small Arms Lethality in Afghanistan:
Taking Back the Infantry Half-Kilometer.
http://www.dtic.mil/cgi-bin/GetTRDoc...c=GetTRDoc.pdf