I have a Encore .50 that likes 300gr. 452 XTP's/crushrib sabot,110 Blackhorn powder. The Encores are basically a sabot shooting rifle, why TC won't say that in their ads.
..just causes new owners to buy more an more bullet combos before finding the sweet load.
If I had to use a powerbelt it would be in the 300 grain range for better penetration. You could cut off the QLA and you might get a better conical shooting barrel also, but then the warranty is voided.
The sabortooth bullets by Harvester are another option, very simular to powerbelts, again 300 grains at least.
Look into an older White or Knight rifle with #11 ignition. They were made for conicals and still work very well.