Bullet seating depth

It’s not likely that you will be able to load 150 or 174 gr .303 spitzer bullets to get within .030 inches of the lands without seating them past magazine length.  To do this, a boat tail bullets will have very little grip from the case.  You will have to single load anything longer than about 3.07”.  It’s somewhat of a compromise with having sufficient length of bullet bearing surface held by the case neck and getting the bullet ogive close to the lands.  Bullets like the Sierra SMK with its tangent ogive are very forgiving of a long jump to the lands, even as much as 0.30 inches off the lands. These barrels typically have long throats and they get longer the more rounds are fired. When I pulled the BSA barrel off my primary shooter, the throat had extended such that the 174 SMK was out of the case neck before it contacted the lands. 

The trick is to use light finger pressure when pushing the bullet into the lands, don’t force it.  

^^^ THIS.

I actually seat so that there is one full caliber diameter in the case neck,excepting any boat tail present & let the length overall fall where it may.

 

Yes its a compromise, but its a working one. When I test seated several different bullets to contact the lands,none of them had enough in the neck to hold, much less stabilize, or center them!

I ignore the cannelure completely!

I don't crimp,& so don't need the cannelure for that & this in turn frees me up to seat to whatever I want.

I have polished down all my expander balls so they give a higher than factory grip on the bullet with the case mouth instead.this has reduced my neck & bullet run out as well, which is a good thing.