The first post was typed on a mobile device in a side beis midrash, thus the weird formatting.
In general, we are machmir if we know there is a claim of sherry casks, even though according to Rav Moshe ZT”L it would be acceptable, just like we are machmir today not to use products where there is bittul beshishim. However, sherry casking is a shevach. Why should we assume they use them if they’re not on the label? No matter what they say in a private letter, they don’t get busted for false advertising unless it’s on the label. So if they don’t advertise it, it’s probably not true. Furthermore, even according to Sherry Cask’s info, they only use 20% sherry casks. They also reuse casks. Furthermore, Star K’s website says they clean out the casks. That has to reduce the amount absorbed into the alleged sherry casks.
Bottom line,
1. Shema ein kan issur klal- if they don’t advertise it, who says they’re using it?
2. If they are using it, who says they’re first-run casks?
3. even if they are using first-run casks, they are cleaned out beforehand.
4. Even if they weren’t cleaned out, beforehand, they don’t use 100% sherry casks, if they are in fact using sherry casks.
5. Even if they were using 100% sherry casks which were uncleaned, they would still be battul besheish according to Rav Moshe ZT”L. As it is, they’re most probably battul beshishim according to the machmirim, if they are, in fact, using sherry casks. A typical barrel holds 50 gallons. There is at least 8 times as much liquid as there is to wood (maybe more- I’m having a rough time figuring out how to Google this). So even if the cask was dirty (which it is NOT), all you need is 8 regular casks to one theoretical uncleaned sherry cask to have bittul beshishim according to the machmirim who follow the Shach.