I recently got around to getting a sling for my USHD, but it seems like the sling swivels dont come out. Am I doing something wrong, or do I have to get a sling that I can feed through the swivels? I can unscrew the whole swivel, but there is no way to get the loop inside the swivel.

Perhaps it was made with NON quick-detachable swivels?

They are notaquick disconnect type. I ran into the same thing on mine. I just un-bent mine, the drilled a hole all the way through the stud and used a set of quick disconnet. Not that hard to do. Just tear the old ones off the studs and you will see what I mean.

You should be able to unscrew the studs from the gun and replace them with new ones that you'll have to purchase. I had to do that and it worked out fine. I was able to put my preferred sling on that way. Can't even tell the difference once you put the correct studs in place of the old ones and you'll be able to have a good sling.