The 'GREEN' debate.
Appeasing the 'Greens' by placing some emphasis on a 'green' round is sensible in this day and age. This is really a minor point as the military ultimately focuses on the job at hand which is defeating the enemy. I wouldn't read into the ground pollution problems too far as I'm sure the 'G' knows that there has been little evidence regarding this, they do have to take all sides into consideration. A bit of smoke and mirrors IMO.
Why is the Marine Corp fielding SOST (Mk 318) and Army M885A1?
There are many examples of the different branches of the military choosing to use different equipment. Take camouflage patterns for example! Armor carriers, armor plates, ear protection, hemostatic agents, tourniquets, CREW devices and the list goes on. The fact that the Marine Corp wants to field the SOST (Mk 318) is at their discretion based upon the types of conflicts they 'typically' find themselves in. The decision was made based around vehicle check points and the USMC's desire to have a round that can penetrate auto-glass IOT stop a potential VBIED from entering the check-point! Okay, so what about 90% of the other marines that are facing the enemy in the open? On patrol through AFG you will engage the enemy more times outside of a vehicle than you will inside one! Also if you need barrier penetration, you need only send a fire control order to the SAW gunner, 240 gunner or send a 203 HEDP, 66, 84, .50 Browning, MK19, A10, JDAM, or any other barrier penetrator in the inventory to achieve the aim or desired effect. I would much rather have a round that is capable of quickly incapacitating the enemy when directly striking him rather than a round that is specifically designed to penetrate then incapacitate. Wasn't that the issue with M855?
Time to Change!
All branches of the military need to rapidly change doctrine, methodology, TTP's and equipment if they want to remain relevant in today style of warfare. The U.S military has been guilty of this in the past. There is no need to bring up examples of previous engagements that resulted in a poor battle plan due to the type of warfare being conducted and a lack of TTP's to deal with it.
Trijicon may have to come out with another reticle designed for a different trajectory, M68's don't have this issue. As warfare changes, equipment needs to change with it. The zero of weapon systems is not that big of a deal. Weapons ideally should be zeroed to the ammo being used. Although I don't know off hand the POI shift between the two rounds being fielded, I don't think that it is significant enough for a soldier or marine that struggles with many other factors of poor performance relating to poor down range accuracy. The marksmanship standards are loose enough to absorb these minor issues. Over-whelming fire support and suppressive fire will always beat individual marksmanship during an assault. At the closer ranges during CQB and battle-field clearances, the POI shift won't be noticed.
I don't think anyone can honestly look at their pay check and say that they notice money missing due to the expense of the round development. Tax payers money! Wouldn't you prefer to have our troops finally shoot ammo worth shooting at our enemy regardless of the cost?