Very Strange 870 Barrel

[Minshooter]

I have a 18-1/2" 870 barrel, marked manufactured by Mossberg for Remington, with a very strange front end.
The front two inches of the barrel are greatly increased in diameter, and threaded 1-1/16"x20.
An aluminum sleeve is threaded over this, secured by a rear jamb nut & thread sealer.
The sleeve is 1-1/2" diameter and 7" long, with 4 rows of five and six 1/4" holes, staggered spaced along the lower length.
The top of the sleeve has a weaver/picatinny rail, secured by four screws, and a brass bead front sight.
It is finished in a black matte, and looks more like a flamethrower, or the front of a 1919 browning machinegun, than a shotgun barrel
Mossberg was of absolutely zero help, even though they made the barrel.
Has anyone ever heard or seen of these?
I was going to put it in a lathe and remove the oversize threaded portion, making it into a 18-1/2" cylinder bore barrel,
but in case it has some obscure purpose or value, I thought I'd ask here first.
Thanks
Once I figure out how to post photos, I'll do that.
First and only one I've ever seen.

[BKinzey]

Pics will be interesting. I'm not familiar with what you are describing. Don't think I've seen one.

In order to add a pic to your post look below the reply window. There are 2 tabs, Options and Attachments. Select Attachments and click on Add files. Then you can add a pic, under 2mb, to your post. Once the file is selected I also click on Place inline so the pic appears in the post and not as an attachment.

[Minshooter]

Thanks.
I will post a photo as soon as I can figure out more of this new laptop.