just took my own advice

[bruce moulds]

semtav,
with bore + 0.001 bullets, I can use a palm seater.
for groove diameter bullets, a weber type seater would work better.
bullets would possibly slide in better lubed with tallow?
make no mistake, when you get that gap right you will be impressed.
all my scheutzen friends do this with greasers at groove diameter.
mostly 38/55. this chambering often requires a smaller airgap than 40 and 45 cals.
you might try starting the bullet as you suggested, then finishing it with a case containing a wooden plug which extends 1/8" past the front of the case.
an important consideration is not to bump up the bullet as you drive it in, so using a hammer might not work.
keep safe,
bruce.