The only one of my AR's that doesn't do that very same thing is my 6.8. The rest do it even from mag load though, as NoMercy pointed out, not as bad. I have a standard pin in my 6.8 so I have no clue why it doesn't do that. I know the first few times I went to eject an unfired round and saw that I was seriously questioning it myself. Just do what NoMercy suggested and ride the bolt a little and also make 100% certain of your muzzle direction when loading which you should always do anyway.