Just got back from mackerel fishing. Now its time to watch Lone Survivor for the third time..
Follow along with the video below to see how to install our site as a web app on your home screen.
Note: This feature may not be available in some browsers.
http://en.wikipedia.org/wiki/Close_Quarters_Battle_Receiver
The SOPMOD Block 1/2 kits are mostly off the shelf parts kits, but as JCheese says the MK18 Mod O and Mod 1 are the Navy designations for the CQBR (although the CQBR itself is a modified M4 and has since been removed from the SOPMOD programme and has a development program in its own right). Block 1 and 2 aren't better or worse either, just that Block 2 has some newer bits.