AR receiver 6.8 / .556 differences?

[In2b8u]

I know that the 6.8spcII has proprietary mags. I am checking to see if they are dimensionally the same (with standard ar lowers), and what makes the spcII mags different? Thank you in advance.

 

[blackblue]

Lowers are the same.

 

[Hogshooter]

Difference in the mags from 5.56 is that the follower is slightly different and the feed lips are a slightly different configuration.

 

[In2b8u]

Thank you both. Much appreciated

 

[vmpglenn]

Difference in the mags from 5.56 is that the follower is slightly different and the feed lips are a slightly different configuration.

Mag ribs on 6.8 mags are also shallower, and mag bodies will invariably be made of stainless steel because Al mag bodies bulge too much.

 

[rusty815]

Only differences between 6.8 rifles and 5.56 rifles are the mags, bolts and barrels, everything else is the same. I remember reading somewhere on the 68 forums that 68 mags can be made to work with 5.56 rounds, but not much info on that.