I voted 6.8 since that's what I own. I also ordered a 6.5 kit. Down the road I may decide to sell which ever one I shoot least since the two cals are relatively similar under 100yds which is the range I shoot most often.
It really depends on the intended application of course. I got mine mostly for plinking but at close to $1 per round that goes against convention. I also wanted something with enough muscle to hunt with if I chose to. A 5.56 may be good enough for a soft headed zombie but bigger, hardier game may prove to be more challenging without precise shot placement. And precision isn't exactly something these platforms are famous for.
Me personal, I would start with 5.56 due to the wide availability of ammunition and magazines and the rounds known characteristics then go with 6.5 RA conversion kit later. Anything the 6.8 does the 6.5 does also. After 300 yards the 6.5 really starts to out shineshine other calibers with higher retained velocities and flatter trajectories. The 7.62 NATO round goes sub sonic at around roughly 800 yards,the 6.5 is still supersonic out to roughly 1,100. Not that I ever plan on shooting that far but it is nice J.I.C. There is a wide variety of 6.5 bullets for the hand loader too. Its nice to know that 6.5 bullets of comparable weights and velocities have been performing well on big game for decades.6.5 bullets also worked well in military applications for a long time for Sweden,Japan and Italy. David Tubb and others have had some notable success with them in matches as well. The 6.5 has the same case head dimensions as the 7.62 x 39 so adding that caliber will just require a barrel and magazines.
I am not "dissing" on the 6.8 the 7.62 or anything else here. just stating the line of logic that lead to my conclusion.
If you're going to shoot a lot and train in carbine classes etc, 5.56 is the way to go due to cost and ammo availability. You can always add caliber kits. The exception now is the 7.62x39. If you buy lots of ammo now it's by far the cheapest. The problem is getting mags for it. I'd steer away from 6.8 unless you're hunting or planning a war.
I'd say its mainly personal preference and what the intended purpose of the rifle will be.
My opinion is that if you want a round that you can use for plinking, home defense, or small game hunting, go with the 5.56. Fairly inexpensive bullets and magazines, will keep you shooting longer and cost you less than with the larger calibers.
If your going to be using the rifle to hunt midsize game, i.e. whitetailed deer, mule deer, etc..., choose the larger calibers. Keep in mind availability and price of ammo and magazines.
I myself opted for a 5.56 model, mainly because it is the only caliber that my department will authorize and I can shoot it for free. I would love to have it in 7.62 NATO, but under the above circumstances and the price of ammo, it would be more of a safe queen than anything. Theres no fun in having a rifle that you cannot afford to shoot and have a good time with. Just my :2cents:
I just bought my first two XCR's. I bought both in the 5.56 because it is cheaper to buy this gun then the others and the conversion kits cost the same. So I decided when I want to buy a conversion kit, I will probably pick up the 6.5 and maybe the 7.62 (cost of ammo is getting cheaper in the bulk for the 7.62).
If you DON't reload go with the 7.62x39, it's cheap and legal on deer and such to a max of 200 - 300 meters (depending how well you shoot). If you DO reload go with the 6.8 or 6.5, might cost more to feed but both will legally take medium size game. If you plan on long range engagement(s) go with the 6.5. :2cents:
Thanks everybody for all of your input. Much appreciated to hear it from the source!
I've decided to go with the 5.56 for a couple of reasons. First, the ammo is less expensive and more available than the 6.8. Stocking up on magazines will be easier too. If i get into reloading, I'll buy the conversion kit to 6.8 and start reloading that round. Reading the ballistic reports, it seems the 6.8 is a much better all around round to kill zombies At around $1 per round, i just cant justify that for plinking around.
Also, the 5.56 XCR seems to be more readily produced by Robinson. However, after calling around to almost every dealer in the US, nothing is available right now! Doug's Shoot and Sports in UT sold their last 5.56 w/ folding stock yesterday and thats the model im looking for. They are offering it at a reasonable $1500 with no state tax! I live in WA, so after the transfer fees, im looking at around $1550 total. Does anybody know of another dealer with that model in stock?
I just called Frank. He's all out too. He said Discount is receiving about 12 XCR's at the end of December. Get this, already 9 of them are pre-sold! He's selling the 5.56 heavy barrel, folding stock for $1699 plus tax (thank you WA Democrats). Price seems high, but thats just because of the extremely high demand now.