Re: 308 blr
I load Sierra 175's (BTHP) for my .308 using neck sizing only, and I always follow up the seating with a slight crimp. There's no crimp ring on that particular bullet, but using the Lee factory crimp applies a taper crimp opposed to a roll crimp, and it works out good for me.
If you haven't been crimping, and it's working out well for you, and if you're getting the accuracy, and consistency you want.... I guess if it ain't broke.... why screw with it.... If on the other hand, you do decide to give it a try... look at other factors... chamber fit... shooting C.O.A.L. as opposed to shooting off the rifling, etc..... watch for pressure signs, adjust your charges if necessary, follow Lee's recommendations for using the crimp, and most of all be safe....