Unfortunately, I'm not sure my schedule permits attending any of the "events" at Rachels this week while I'm here at SHOT, so sorry DC2.
But I did partially answer the mail on the whole 6.8 question. Though I'm not sure how much more light I can shed on the subject since it just seems to me a technical question of ballistics, range and penetration with a more macro question of where this round fits -- or could fit -- in the US (or international) arsenal.
I had a long conversation with Jeff Clemmer, a program manager with LWRC International. Reason I talked with Jeff is that his company's PSD Carbine is chambered for the 6.8mm SPC round and has become increasingly popular with the private security community and some government agencies.
Jeff gave the some gouge on the advantages of the 6.8mm round. He told me that during the congressional test shoot in July, staffers were amazed at the performance of the round at long ranges.
"When we fired the 5.56 to a steel target at 300 yards, rounds were just pinging off," Clemmer said. "But the 6.8 was knocking them flat."
I'm no expert, but 300 yards is a pretty good distance for a carbine...and they were shooting the 6.8 during the demo out of the PSD which has an 8-inch barrel.
Ballistic demonstrations with jelly showed better penetration at those ranges than the 5.56 as well, Clemmer said, and published reports confirm his field data.
I asked about the added weight. As you can see from the picture here, the round is only slightly fatter than the 5.56 and significantly smaller than the 7.62. He said a standard 30-round magazine holds 25 rounds and offers a negligible weight penalty.
But given all the positive press on the 6.8, there's one huge problem. It's a whole new round.
It's clear to the folks at LWRC how difficult it would ever be to convince the institutional Army or Marine Corps to make a hard right turn and change the standard-issued carbine to a 6.8mm one. So I asked him why they still make weapons chambered for 6.8 and he said the round was becoming increasingly popular in the private security community and, oddly enough, the hunting crowd which likes to use a military-esque round for plinking varmints and such.
I did ask him about the 6.5 Grendel round as well and he said that there just aren't that many weapons chambered in 6.5 (I don't know how accurate that is) and that the manufacturing base is small as well. He didn't have anything bad to say about the round, though, adding that the ballistics are only slightly different from the 6.8.