04-25-2014, 08:08 PM
If you mean my 6mm Optimum (below), one of the drawbacks that come to mind is the same as for 6.5 Grendel and 6.5 GPC: Increased weight and size relative to 5.56 NATO.
Another, perhaps more important issue, is that barrel life would likely be very low.
![[Image: Jul_31_001.jpg]](http://www.g2mil.com/Jul_31_001.jpg)
Another, perhaps more important issue, is that barrel life would likely be very low.