Title says it all.

These barrels are unobtainable, even through using Chest Upgrades, and even looking through the source of the mod itself there are no recipes. This might be a WIP, in which case I believe they should be hidden from REI. Definitely just an enhancement, but a welcome one.

This is an issue for the Ironchests Mod, if I were you I would close the Issue here and open one in the other repository since this issue has nothing to do with this modpack.

But I agree, having these would be kind of cool ^^

This modpack, however, can label those as REI hidden as it does with the unified ores and such so this issue can still apply to the pack

I added a PR for IronChests to add recipes for the barrels. Maybe it will be accepted even if there are no upgrade items for the barrels yet.