They have a submissions call out for short stories, but other than their website and FB page, I can't see much out there about them.
Anyone dealt with them before?
https://www.castrumpress.com
https://www.facebook.com/castrumpress/
Paul Corcoran is a person publicly associated with them.
https://www.facebook.com/PaulCorcoranAuthor
I've had no personal experience with them or ever heard of them, but I did check the website. They have several authors listed, but at least some of them are anthology-only. (Christopher Nuttall, for example, is on their author list but is only represented in three of their anthologies. He's very hybrid, with a huge number of titles, some self-published, some published through small publishers, but most of his output isn't military sci-fi.)
Clicking the retailers link takes one to a series of Amazon listings--oddly, this publisher doesn't seem to go wide with its titles. I only looked at a couple of books, but they have few reviews and are sitting around the one million mark. Oh, I see at least one exception: newest anthology (August) is at 133,000.
Nothing obviously screams scam, but it's curious the publisher didn't want to (or didn't have enough clout with Amazon to) negotiate a deal that would let the books be in KU AND wide.
I would say this is a small publishing operation.
