 They should be pretty close to subsonic at that level. Here's the challenge. The published threads on the muzzle, and I'm making this up, but it's like .575 by 28. And don't quote me on those numbers. But whatever the published one is, I bought the adapter, but it won't screw onto the carbate. So I've got to have a gunsmith or something look at it because they publish that that's the correct threads.