In looking for a sub load for my .416 Rigby and cast 350 grain Flat Nose Boolits, I found some loads listed by Hodgdon for Trail Boss (TB).

Start: 25 grains for 1,139 fps
Max: 35 grains for 1,354 fps

I sent an email to ADI who confirmed this is the technique for useing TB.

http://www.hodgdon.com/PDF/Trail-Boss-data.pdf

I managed to score a container of TB from my local gun shop. I weighed a clean empty .416 Rigby case with an old primer in-situ. Weight was 360.80 grains. I then filled the case with TB to the approx. base of the neck. The case holds 35.6 grains of TB. 70% of that is 24.92 grains. Almost exactly the start load on the Hodgdon site.

Old news for some, but sub loads for Big Bores are doable with ADI Trail Boss.

I loaded up one round with 30 grains of Trail Boss under a 400 grain Hornady RNSP Interlock and fired it off this arvo.

Recoil was equivalent to a .243.
Noise was a bit of a dissapointment, more like a Pop from a sideshow-alley air rifle.
POI unknown.
Primer very rounded with no pressure signs.

Full load development tomorrow, weather permitting.

FWIW. 50x .416 Hornady 400 grain RNSP's cost the same as 50x .416 Woodleigh 450 RNSP's A$62 per 50.