I'd jacket them in copper via electroforming for a few minutes for better heat transfer and less shock deformation on firing. i.e. the copper jacket would take the beating not the aluminum round. Depends on your tolerances though.
Ensure you are using jigs and not eyeballing things like alignment of the sabot. Ensure your jigs are trued. A tiny deviation will cause completely different effects at the Mach number of muzzle velocity = zero repeatability between rounds.
>it was LOUD. Probably 10-20% louder than the lead versions
Welcome to supersonic shock waves! The aluminum is lighter so goes faster for the same energy.
>second it seems like it was pretty accurate,
See comment above on repeatability.
>it was pretty damn powerful.
IIRC your basic form is similar to a pellet round that is used to destroy varmints. Hydro-static shock etc...
I'd never put those in my barrel. See the central penetrator pointing off the longitudinal axis in that last photo? That could gouge the barrel leading to catastrophic failure, particularly if the tolerances aren't tight and round yaws on firing given there are no gas bands.
Good idea, just needs finishing like polishing, truing. Two of the same rounds should look like twins - you can't tell which is which. However, yours currently look like cousins.
Godspeed anon & fuck the ATF