yeah, as BB said the forces relative to the area for glueing are very low.. so make the brass sleeve a tight fit and glue / loctite it in. Just be sure to degrease thoroughly first.

I'd go with 3.0 - 3.2 - I've just reamed my 80 TP to 3.1 and it shoots very nice at 11 fp - but this is going to be running near 16 when I export it. 4mm is too big for any power level.