If you are shooting a bolt action rifle then for sure no need to crimp. The neck tension is plenty good enough. In handgun cartridges you want to crimp because you are expanding teh case mouth to ease insertion of the bullet. With rifle cartridges you do NOT expand the case mouth so no need to crimp it back down. Magnum revolvers you want a firm crimp to prevent the bullet sliding out and jamming the cylinder.
Plus in the handgun cartridges a little bullet setback can cause a dramatic increase in pressure. Not so in rifle cartridges. The case is much bigger so the ratio of volume displaced by set back is much smaller compared to handgun cases.
Even in a semi-auto crimping often is not necessary. I load for AR15 and M1 Garand and have never had a problem with uncrimped bullets. They do get slammed pretty good on the feedramp so if you want to crimp it may be a good thing to reduce any stoppages. If you load with a bulky slower powder that is compressed (such as Varget or H4895 in .223) then you definitely won't have bullet setback.
I don't think there is any safety concern regarding significant pressure changes. If you are loading for bolt action then no reason to crimp at all. If loading for semi-auto I would not start off crimping and see jhow it works in your rifle first. Chances are it will feed just fine without crimping.
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