The problem is in not knowing what another individual who is successful with his target loads is feeling when he seats a primer. Some folks with some equipment are going to generally hit the sweet spot whether they intended to or not. Not knowing who those folks are means not knowing what role that did or didn't play in their championship success.
Naval Ordnance at Indian Head studied primer seating and refined the targeted range of reconsolidation of small and large primers used in military munitions from the 0.002"-0.006" number originally recommended by Olin and Remington to 0.002"-0.004" for primers from those same companies. They want ammunition that works reliably from -65°F up to desert temperatures rather than peak accuracy in most instances, and that is affected by optimum seating. But that also means ignition regularity is affected by it.
In the mid-'90s, Federal recommended 0.002" for their small rifle and 0.003" for their large rifle primers. I've not heard of any change in that recommendation. I mention it to point out there is some brand variation here due to differences in primer sensitivity.
The same thing that produces the tighter velocity spreads mentioned by Dan Hackett (and we don't know what he was feeling when he seated a primer "hard", or what tool he was priming with) is also reducing variation in ignition time from the firing pin strike to the bullet exit. Since no shooter holds perfectly still, that can sometimes result in the muzzle being directed in slightly different directions at the moment the bullet departs. If, say, one shot spends half a millisecond getting the powder to burn and the next takes five milliseconds to do it, the motion of the muzzle can open groups up pretty significantly. The shooter won't be able to discern that small delay other than by group size, and there are lots of different causes that affect group size, so he may be spinning his heels for quite a time trying to find it.
That last point is why I use the fancy tools when I am working up a new load. I want to get all the variables out. I can then drop the extra effort items one-at-a-time to see if my groups start to open up as a result. If I still get great precision without any special effort or precautions, I consider that a great load, as it will be relatively immune to any variables in my loading process.
Naval Ordnance at Indian Head studied primer seating and refined the targeted range of reconsolidation of small and large primers used in military munitions from the 0.002"-0.006" number originally recommended by Olin and Remington to 0.002"-0.004" for primers from those same companies. They want ammunition that works reliably from -65°F up to desert temperatures rather than peak accuracy in most instances, and that is affected by optimum seating. But that also means ignition regularity is affected by it.
In the mid-'90s, Federal recommended 0.002" for their small rifle and 0.003" for their large rifle primers. I've not heard of any change in that recommendation. I mention it to point out there is some brand variation here due to differences in primer sensitivity.
The same thing that produces the tighter velocity spreads mentioned by Dan Hackett (and we don't know what he was feeling when he seated a primer "hard", or what tool he was priming with) is also reducing variation in ignition time from the firing pin strike to the bullet exit. Since no shooter holds perfectly still, that can sometimes result in the muzzle being directed in slightly different directions at the moment the bullet departs. If, say, one shot spends half a millisecond getting the powder to burn and the next takes five milliseconds to do it, the motion of the muzzle can open groups up pretty significantly. The shooter won't be able to discern that small delay other than by group size, and there are lots of different causes that affect group size, so he may be spinning his heels for quite a time trying to find it.
That last point is why I use the fancy tools when I am working up a new load. I want to get all the variables out. I can then drop the extra effort items one-at-a-time to see if my groups start to open up as a result. If I still get great precision without any special effort or precautions, I consider that a great load, as it will be relatively immune to any variables in my loading process.
