Are you showing pressure signs with that load at 2380fps? Seems a bit slow, even for 130's. I've gotten mid 2400's out of 130's in 16" tubes, and have seen data claiming 2,600 out of 16's. You don't get a LOT with the extra 2", but I think there's more advantage to be gained for the heavy pills. 2,380's pretty mild - I'd be interested to hear if you're really at the top end of your pressure there.
I'm working up some new brews for my BHW 6.8, I'll share once I find a sweet spot. Keep in mind, however, that Black Hole barrels use 3P rifling, that tends to run lower pressure and higher velocity, and I'm running a heavy buffer with an adjustable gas block, so you may not be able to match my velocities at safe levels with your Shilen. My "go-to" for 6.8 tends to be H335. Fast and good metering. I'm not going quite as heavy with my bullets these days, have a bunch of the 100 AB's and 110 Vmax's and TTSX's, a few hundred 120SST/Interlock's that I'll be burning up to see what this new barrel likes best.
Here's some more info on the reality I was trying to point out - Speed can never out-run aerodynamics. (stealing Ridge Runner's quote there).
The .323 BC is giving up a lot of aerodynamic disadvantage to the .460 BC Interbond SST, so that 300-400fps advantage is almost completely gone by 300yrds. 400fps difference at the muzzle has already closed to ~180fps by 200yrds, within 100fps of eachother at 300yrds, and they're running equal speed by 400yrds. Only about 1.5" between the two for drop at 250yrds for a 150yrd zero.
So I don't think you're really going to see a super significant difference in expansion at 200-250yrds, other than the general difference in the Interlock and Accubond itself.
Keep in mind - the 130 Interbond SST isn't designed for the 6.8 - it's not made to expand under 2k, so it's not really surprising that it didn't expand for you when it makes contact at 1800fps.