I agree with Bruce completely except for the part about crimping. Done correctly, and as an individual step from bullet seating, crimping has a positive rather than a negative influence, as it uniforms the bullet pull weight when cartridge necks might vary in hardness and when the bullet is seated so the cartridge will run through the magazine, but isn't long enough to touch the lead. The problem is that many novices and some experienced handloaders alike, don't crimp correctly, so the advantage is lost, and the extreme velocity spread increases, and problems with concentricity arise. Until you get your loads so that they chamber without resistance, maybe follow his advice, seat to the crimping groove, without crimping.
It is good that we don't always agree and with the complexity of shooting and making ammunition, there are bound to be discrepancies between methods used and results obtained.
About the time I was starting to reload I used to borrow a book from the library by the British Military, showing the great many experiments they had made with their newly developed 303 cartridge, prior to WW1.
In one experiment they wanted to know the effect of barrel length on performance. So, starting with a full length barrel in the Lee Enfield, they would cut off inch at a time and note the performance.
They kept shortening the barrel until, as they stated, when they chambered a round, the front of the bullet stuck out!
They then said something to the effect that they were amazed to find out when they fired the round, that the front part of the bullet that stuck out of the barrel, had expanded and was larger diameter than it had been before it was fired!
They said this proved that when a cartridge was fired, the rear of the bullet started to move before the front of the bullet moved.
With that proven experiment, carried out by the British military, my common sense mind went to work. If the reaction is so violent when the powder is ignited, that the rear of the bullet moves ahead before the point of the FMJ bullet starts to move, how could a miniscule bit of pressure from crimping have any effect, whatsoever, on the starting of the bullet?
From my reloading I have never had any indication that crimping, or tightness of the bullet in the neck, did indeed have any affect on the bullets flight.
I have sometimes seated a bullet, only to find that it went in extra easy and examination showed a crack in the neck which I hadn't seen. I have fired such a cartridge into a bench rest group and saw no difference in the bullets POI.
I think once I even chronographed such a loose fitting bullet and found no difference in the velocity from the others, but I don't see notes of that event.
So there you go and Boomer, I guess we will just have to agree to disagree on crimping!