just took my own advice

[bruce moulds]

semtav,
while you are breech seating, you are not going the full monte.
the idea is that the case is full, with the wad level with the top of the neck.
in the 2.4" case you will droptube about 100 gns of swiss 1 or 1.5.
the gap is then in front of the chamber.
I would guess that from chamber neck diameter to freebore diameter would be about 0.012 per side.
I would start with the base of the bullet this distance in front of the case, and shoot groups increasing the gap in 0.010 increments, going out to 0.150 gap.
starting the bullet as you do would allow you to finish seating with steve's pusher and increasing length wooden plugs in a case.
in all cases these plugs would extend past the front of the case.
I intend to experiment later putting a felt wad in the airgap, as this would possibly reduce the chance of ringing.
I do suspect that suspicions of ringing using this technique come from urban myths.
local scheutzen shooters have been doing this for over 100 years and happily continue to do so.
shooting against them with fixed ammo is a futile exercise.
keep safe,
bruce.