Help make my WSM feed

I have an old 110 that was a 243 Win. I also had a 300 WSM barrel laying around and a magnum boltface. I turned and threaded the WSM barrel to "small shank" specs and installed the boltface. The WSM cases were too fat for the attached mag box, so I opened up the feed lips a bit w/ a dremel tool. I let the follower alone. Now the top round feeds fine, when it is ejected, rounds 2 & 3 pop out of the mag box.
OK, I took too much off of the left or right side of the mag box (maybe both). How do I fix this?? What parts do I need to make an older 110 SA feed a WSM case??

You need a new box and maybe follower.
Midway has the box for 10.50.
I'm not sure if the followers are the same or not.
Somebody on here will tell you.

Is the box that Midway has the one that "clips" into the receiver??

Controlled feed bolt face and a standing ejector is how the old stagger feed ones were made. If your using the newer push feed "centerfeed" bolt head that could be the problem.