Technically, seating into the rifling is not the same as seating at jam. IMO the correct definition of jam is the maximum length to which a particular bullet may be seated without being pushed back as the bolt is closed, with the neck tension that will be used when loading. Depending on neck tension, engagement, leade angle, and bullet ogive shape there is some range between the point that a bullet with no neck tension is stopped by the rifling, and jam. Within this range there is a lot of room for tuning, that is short of the point where a bullet would be pulled if a live round had to be unchambered. I believe that within the range between jam and touch, seating depths may be accurately described as so many thousandths longer than touch, or so many thousandths shorter than or off jam. When shooter post that they are jammed .010, I think that this is incorrect usage of a term that they have seen but never had properly defined. In this case, I would properly describe the seating depth as .010 longer than touch. If we use words in a standard manner, I think that better understanding will be the result.
When I am loading a single radius, tangent ogive bullet that has an ogive of about 7 radius , like the Watson, 62 gr. (.750 jacket) bullets that I have, I like to start with the marks (mde by the rifling as the round is chambered) about a third to a half as long as they are wide. With pointier bullets , I like much longer marks (longer than wide).
If loading longer than touch is new to you, and you are concerned about pulling bullets if you have to unchamber a loaded round, a little experimenting, with dummy rounds will give you the length of jam, and how far you need to back off of that to insure that bullets will not be pulled. For my varmint rifles I usually start testing .006 to .010 longer than touch, and am usually able to find a workable load within that range. Working within that range,I have never puller a bullet at the neck tensions that I use.
nt