I still haven't experienced a stuck case in my AR. I've been thinking about the shape of the case as compared to the 7.62 x 39. If you compare the two there's an obvious difference in taper. This leads to the banana looking AK mag vs the straighter AR mag. Also, the chamber contact area seems smaller(haven't actually measured this). Common sense would tell me that the 7.62 x39 would lend to easier extraction due to more taper and less surface area in contact with the chamber. AR15's are extremely reliable In their current form. Should the 5.56/.223 round itself be blamed for some of the earlier reliability issues?