Don't be too quick to "not crimp", you did not say what round(s) you were asking about, in a heavy recoiling rifle, 300WM for example, the recoil can and does effect the bullet seating of those rounds in the magazine, in the same way an inertia bullet puller works. A shift in bullet seating depth not only effects accuracy, but more importantly it can cause Dangerous Pressure problems. The light recoiling rounds 223(for example) are not exempt, the "slaping into battery" of a gas gun can and does effect bullet seating depth, first from the bullets impact with loading ramp, and then with sudden stoppage in the chamber. Load a few rounds, mark them for easy ID, and take to range, along with a set of dial calipers, do some measurements, you can learn a lot about what is happening when you do this. You can do the same thing at the bench-minus powder and primer-by allowing the bolt to slam home with a round you've "loaded", the effect will be greater with powder and primer as the weight is higher, but nonetheless there is a pretty good chance you'll me able to measure the difference, and if so, crimp. The lightest crimp that "holds" everything in place is all you need. Remember, bullet pull effects accuracy, keep good notes on the crimp etc, so once you've found a great load, you can easily duplicate it!
