Via Anthony Williams' superb forum comes a report from Janes Defense Weekly that the US has delayed acquisition of the new small arms replacements for at least 5 years. In the meantime the Army is ordering off the shelf weapons to replace those worn out by hard use in the current unpleasantness.
While this is almost certainly in part a cost cutting measure, I do wonder if at least some of the rationale behind this decision might be an attempt to take advantage of several emerging technologies that might be coming to fruition in the next 5 years or so.
I don't think we're on the cusp of a breakthrough in lasers, though recent advances in supercapacitors might indeed show the way to make them make them practical eventually, (if they have any real world advantages in a dusty environment like a battlefield) so what might they hold out for?
This is purely speculative and way above my paygrade but lets geek this for a moment..
One simple thing might be a new caliber, like the 6.5 Grendel intermediate cartridge. This would be a tough changeover logistically in wartime despite its long term advantages. (IF it performs s advertised it could replace both the 7.62 NATO and 5.56 NATO rounds with a round that has better hitting power than the latter and slightly better long range ballistics than both) one common round would simplify logistics both tactically and strategically in the long run as well as provide an improvement in long range performance and possibly close quarters hitting power.
Another possible breakthrough that they might want to hold off the big weapons upgrade for could be caseless ammunition. The army has been interested in this since the '80's at least as it would greatly lighten the load carried by a soldier as you remove the brass cases...which add up after a few hundred rounds. The downside is that the propellant is exposed to all the grime of the battlefield, it might break or crumble and it has to fire wet....all potential reliability issues. (soldiers can save on weight by going into battle with swords too but I don't recommend it).
Despite these daunting problems H&K claimed to have solved them by the late 80's with their G-11
which was very nearly adopted by the German Army (and is rumored to have been operational in their special forces briefly) but the expensive changeover to unique ordinance not supported by the USA was deemed not cost effective after the fall of the Berlin wall and the costly process of reunification. The rifle has reared its streamlined plastic head a few other times, most notably in the US Army's Advanced Combat Rifle Competition, but it is not in service anywhere.
The US Army is still interested as attested to in this Defensetech article which includes this link to a PDF on a prototype caseless LMG that is supposed to be tested later this year.
I also scrounged up the below picture of an Army concept for a caseless assault rifle from this site. Given that it is from a time when the XM-8 and OICW were the next big things this is likely not a completely up to date image but it is interesting.
Note the lack of any obvious magazine, and that the "picatinny rail" would seem to preclude the use of the G-11 style top loading ammo strips. My guess is that this concept uses an in-stock magazine like the LMG11 pictured below.
Another possibility could be polymer cased ammo as referred to in this Defense Review article. This would give nearly all the advantages of caseless without the exposed propellant problems.Like an intermediate cartridge the advantages would warrant a new rifle orLMG, though again this would be a cast iron bear to do in the middle of a war.
Though not explicity mentioned I suspect that dramatically lightening the case-end of a cartridge might adversly affect its feeding properties such that magazines and possibly feed systems might need to be changed, another short term logistical hurdle even if otherwise identical cartridges are used. Quite aside from my out-of-expertise hypothesizing, there have reportedly been some issues with this recently. I must say though that given the pace of progress in material science they look to be eminently beatable....
...perhaps in 5 years time?
UPDATE: A reader E-mailed me to tell me, amongst other things, that I am off base regards the feed reliability of polymer cased ammo. There are, it seems already commercial versions on the market that feed reliably with NO modification whatsoever. The person in question is in a position to know what he's talking about.
The same E-mailer asks what happened to the 6.8 SPC round? That is a good question, it was reportedly getting rave reviews from spec-ops people in Afganistan, and then just sort of dropped off the radar.
It may be that the rise of the 6.5 Grendel which has the range of the 7.62 NATO and can fit in an AR-15 length action may have displaced it as that round could (in theory) replace both 5.56mm and 7.62mm rounds in new weapons. Airborne Combat Engineer has a comparison of the two rounds here.