I had thought about crimping when I made my 35 Whelen AI, but decided it was too much of a hassle. If the case lengths are not the same, then you will have uneven crimping pressure from case to case. Thus your chamber pressure will also change. If you crimp with a seating die, then the crimping process starts before the bullet is completely seated and you're damaging the bullet. So then you have to get a seating die and add one more step to your loading routine. I have never had a problem with the Whelen, nor my 375 H&H.
Since you are shooting an AR, the greater problem is the bullet moving forward as it is slammed into the chamber. Again, I have not had any problems with my ARs, including my Grendel and 7mm Valkyrie where I turn the necks lighlty to remove any high spots.