Sorry, I have more questions than answers. (some to satisfy my curiosity and some you should want to have answered)
Came across them, how?
Are they chambered or just threaded?
What brand barrels are they?
You'll have to determine if they're of high enough quality to throw a little money around to get them on a rifle....if that's your goal.
Have a qualified "smith" check the thread pitch and they can tell you what they might fit.
Zeke