M468 assault rifle. I forgot if that's it's name or not. It's essentially an M4 with the 6.8mm round. I've actually looked up on wikipedia what its kinetic energy was. My conclusion, it hits harder than an AK47. It also has been described as having "only slightly sharper recoil" when compared to m4s.
There are a couple different weapons of the "AR" lineage chambered for the Remmington 6.8 SPC.
My favorite is the Adaptive Combat Rifle (ACR):
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There is also an M4 series rifle chambered for 6.8mm rounds made by Bushmaster:
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Ah... apparently this picture does some of the work I'm about to do for me:
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Realistically, I would choose an ACR. If I am allowed to carry attachments/extras, I'd bring the 6.8mm barrel and attachments along with the 5.56 being my standard loadout (ammunition more common).
If I am not, then I would simply stick with the 5.56 in a 10.5" barrel with the foldable stock. Enough power to reach out across a parking lot, but still agile enough to use in confined spaces. Though I would definitely want some kind of melee attachment for the rails - a hatchet, bayonet, ... miniature chainsaw... something.
