The OICW is the US Mil's latest attempt to field a Buck Rogers do-everything rifle, & the system's weight - about 17 lbs unloaded - shows it. Its combination grenade launcher w/ an underslung carbine is the reverse of the M4/M203 combo (a carbine w/ an underslung grenade launcher). In this case, the grenade launcher, & not the gun, is the primary system (Caveat emptor: the gun can be detached & used independantly of the launcher).
It's basically a G36C overslung w/a sophisticated target acquisition device, firing specially chipped 20mm burst rounds that are instantaneously programmed by the targeting device in real-time to detonate correctly on target for max effect. It is touted as another troop tool to supplement to the std. M4 - not a replacement for it. However, in the final analysis, it'll probably end up being just another expensive & excessively complicated (The operation manual alone is roughly 1" thick) DOD pork bbl. project.
Edited for punctuation, grammer, & to concur w/ others regarding the 10" bbl. & bayonet mounting. The snowboard feature might come in useful in snow-bound environments, allowing the operator to make a hasty retreat after s/he is exhausted from carrying it, running out of HE clips for the same reason. Maybe the bayonet is an admission to the system's inevitable failure; better to ready the operator for the inevitable CQB. Of course, it'll be interesting to witness its actual use in close-up, melee combat.
I'll keep my M4, thankyou.