First of all the 5.56 "was" much easier to get than the 6.8 SPC (Special Purpose Cartridge). However with all that is going on that has certainly changed as of late. You would probably more likely find a box of 6.8 SPC on the shelf before you will find any 223 or 5.56 NATO. You in normal conditions, could find more bulk 223 or 5.56 NATO than ever find that quantity of 6.8. And was for less money! But supply and demand is upon us!!!!
Maybe for the 223 or 5.56 NATO things will calm down and it will become a little more like normal in the future. However the way things are going I have my doubts. Of Course one can always reload as I do for my 6.5 Grendel AR. Preempting the following info I also have several 223 Rem/5.56 Rifles and I like them as well!
As far as comparing the 6.8 SPC with the 5.56 NATO. The comparison depends on the purpose of the specific round. The 5.56 is flatter shooting but has less ft. lbs at range and is effected more by wind than the 6.8.
The 6.8 as far as effectiveness in actual combat or defense is superior to the 5.56 or 223 Rem. The 6.8 is 44% more energy than the 5.56 and in the government tests out performed the 7.62X39 round. If you go on line and Google 5.56 vs 6.8 SPC there is a video there where a guy is shooting water jugs. You will have no doubt of the difference in ft lbs of energy if you watch it. The 6.8 has 1754 ft. lbs of energy while the 5.56 NATO has 1325 ft. lbs of energy. It is 27 cal.
(.270) compared to 22 cal (.223). This comparison is based on the 115 grain bullet of the 6.8 to the 5.56's 62 grain bullet. I have hunted with both and the 6.8 will bring down a coyote, pig, as well as deer much more quicker and effectively than the 5.56. Although I have had success with both, I would not recommend the 5.56 for deer from experience. The other real benefit of both is that if a person has a standard AR-15 complete lower they can switch back and forth and have two different calibers. The complete 6.8 SPC Upper along with the 6.8 Magazine will work great. And one could obviously go back to his original set up of the 223/5.56. By the way normally the 6.8 magazine has a Blue Follower in it so you can see readily which mag you have without having to look at the writing on the side. I guess it boils down to the use and your personal preference of the two calibers. Both are good calibers but the 6.8 SPC was the preferred round for combat by the Arm Marksmanship Unit and the Special Forces Units involved in the tests. There are some Special Forces Units who prefer it highly over the 5.56 and are presently using it today in combat.
Ok great response .. I have seen the video ..I liked it and I've seen video on ballistics gel on both rounds..but to solve the problem of deer hunting ..use my standard .223/5.56 bottom and attach a 6.8 upper ? And everything fine correct? Again thanks for the response.