RCBS makes + size shell holders For 308, and 223 based cartridges that can give you some extra headspace when resizing brass as well, but I’m not sure they would work for your application.
Yeah, and so does Redding. But you don't need special shell holders, just adjust the die for the right amount of shoulder bump and be done with it.
IMO .012" headspace is a lot, but not as uncommon as many people think. I've seen worse than that from following the directions of FL dies in some cartridges; I'd wager there are a lot of people here on the 'fire who are sizing their brass to that much headspace or more and don't know it.
If you are planning to reload that brass, just make sure to adjust for the right amount of shoulder bump (.001-.002" is good). If you don't load your own and are just shooting factory ammo, honestly it's probably ok to just keep shooting it as-is.
