I'd say he's holding the m249. Looks like it has a longer barrel judging by the side views.
Also it says full size in the description for the m249 while it says near full size for the m248.
Regarding which surefire he uses at the end. I found some nice screencaps =)
I was confused for a while before realizing that the light switches from left to right side here and there in the film. But I believe it also is the m961, newer than the one on his hk416 but older than the m961xm07...
I'm also putting a replica together of connors hk416. Yours is looking great!
I'm having trouble finding the surefire for the 416. It is a early version m961 right? Can you help me with a source??
Also I notice that you are true to the movie in using the front flip up that is meant to be...