Drew,
With all due respect, if a sleeved gun had a joint that fit like the dovetail at the picture of the front end of those lumps, nobody would buy it. It is sloppy in the extreme. It could have been made to fit perfectly.

It wasn't.

Dewey didn't wake up one day and, off the top of his head, decide he didn't like Winchester 21s.

He got sick of working on junk. He fixed a lot of it when he had to.

Now, he doesn't have to.

Best,
Ted