I have to agree with that. I really don't see where bullet seating depth will enter into things until the bigger factors are done and that would be what powder with your bullet choice. The powder ans amount of powder first and then bullet jump. Just my take on the subject but I agree with murf. Ron
I agree with both Ron and Murf. It is a simple matter of cause and effect and it is with great amusement that I note (where I live at least) that jump is considered to be the holy grail of final group reduction. You get your load close and then tweak the jump for perfection.
So what happens when we tweak the jump, two things;
The first is that we alter the internal volume of the case thereby altering the internal pressure / velocity / elapsed barrel time.
The second is that we reduce / increase the inertia that the bullet requires to overcome the lands.
So changing the jump (not talking about high precision shooters here who seat into the lands) simply is a method of altering the load. So where some people are very close to an accuracy node a change either way in the jump could be sufficient to bring them onto an accuracy node. Now when you bear in mind that pressure lifts rather exponentially as you approach the lands then you will understand that you can significantly alter the characteristics of the load in question. In my opinion chasing the lands as a means of altering load is not the safest reloading practice.
Now there is a definite point at which the relationship between internal pressure and inertia. I believe that there are many misconceptions about the interplay between the two. All things being equal, if you have an extremely long leade, then as you seat the bullet further out you increase the internal volume of the case and you reduce the pressure and consequently the velocity.
Now this would be all good and well if we had a long lead but most rifles simply are not designed that way so we have to contend with the lands. An herein lays the rub. There is a point where the reducing pressure in the case as one seats further out is reduced / offset by the increasing effect of inertia.
After numerous debates on local forums on the matter I went out to test the theory. At the time I was doing load development for a friends 7.62mm Israeli Mauser. So to the OP the calibre is the same so probably very relevant to your current situation.
I prepared a series of loads with the only variable being the proximity to the lands. So I loaded at 2.00mm (0.080") from the lands coming down in 0.008" step until 0.008" off the lands.
I shot 3 shots per jump and averaged out the speed. I then fed the speed into QL and arrived at a pressure. I then for each group modelled the QL calculated pressure, take note QL does not take into account the effect of inertia other than when you are directly into the lands. So this is the plot;
The blue trace is the theoretical pressure and the red trace is the pressure based on the actual recorded velocities. What is also apparent is that at 0.040" that the effect of inertia is being experienced.
So while a change in jump may well close a group it is my considered opinion that this is not due to the distance from the lands but rather due to the change in the ballistic profile from the combination of internal pressure and inertia.
I would, for a hunting load, encourage staying away from the lands and loading just short of the magazine length so that cycling a new round into the chamber never becomes an issue, normally not a problem with a 30-06 due to the action length.
I shoot 180gr. Accubonds as my primary 30-06 hunting load at 0.080" from the lands (only because I saw an article on this as a recommendation). I shoot consistent 0.75MOA groups and I am not a great shot. 180gr. SGK's I shoot 0.040" from the lands and get slightly better grouping but I have found Sierra's weight for weight to be more accurate than Accubonds, if only by a small margin. This I have found with 140gr. (6.5x55mm), 180gr. (30-06) and 300gr. (.375).
One final argument for jump. On my .375 I cannot get to within 0.250" from the lands, here is a group I shot with 300gr. SGK's.
Now granted I can't repeat this 0.240MOA shooting every time I pick up the rifle but if jump was so crucial then explain how being so far from the lands could yield such results?