6.8 / 5.56 interchangability

[Gump]

This is probably a simple and repeated question, but I can't find the answer. If I buy a 6.8 rifle, will I be able to swap in my 5.56 upper and magazine to shoot 556? Do the two calibers use the same spring and buffer? Are there any problems switching back and forth?
Thanks
Gump

[musashi666]

You should be fine swapping the uppers out. Some may tell you you may need a H-Buffer with a CAR tube but I have used a standard buffer w/ my 6.8 and not had any problems so far.

[FlyingHunter]

I've had zero problems switching 68.and 5.56 uppers on the same lower. I use two different Colt lowers.

[Stephen_H]

No issues.

Stephen