Last weekend, I was out testing some loads at the range - in spite of the pretty serious wind blowing, a guesstimate of around 30mph tailwind, wiggling around occasionally is justabout every direction - I even saw some patches blowing back...
Still, I needed to test some loads for the upcoming french match  - this time a .450 1:16 510gr bullet patched up to .458 in front of 75grs of 1 1/2Fg Swiss - a pretty much zero compression load, the bullet seated to barely touch the rilfing.
In spite of the winds - and me forgetting the rifle's sling  (luckily I had an alternative on hand), results were pretty encouraging at 200m.
Yes, the bullet takes up quite a bit of powder space - the complete case neck, more specifically.  But that was the intention - I need the load to perform out to 300m, although I'm pretty sure it will do equally well at longer ranges.
As usual, shooting was prone, with sling, no support.  I actually was surprised at the accuracy I got in that shifty 6 o'clock wind - sometimes, the gusts were so heavy  I saw the front sight move with the gusts when aiming...

Some trigger work might be required though - this is my 1st no.2 Musket match rifle, and the trigger is a pretty healthy 3+ pound.  2 Pounds would be quite a bit easier to shoot well...  Some gunsmithing work ahead.