There's no need in crimping these big bore AR calibers. I don't crimp any of my 458 SOCOM loads.
I don't know about the Lee 50 Beowulf dies,but with the 458 SC,you can't seat & crimp the bullet at the same time. You have to seat the bullet,and then adjust the die to crimp the case.
I rarely crimp any rifle cases,if your sizing dies are set up correctly,you will have plenty of neck tension holding the bullets in the case. If your loading for a tube type magazine (30-30),then you really need to crimp the bullets in the case to prevent bullet movement in the case,but with a magazine like the AR I've never crimped bullets.