Here is a rifled barrel on E bay for $50.00.

http://www.ebay.com/itm/WEATHERBY-12...item1a059b892c

Carlson choke fit chart for Weatherby
Weatherby: Interchanges with Winchester, Mossberg 500 and Weatherby style threads. $44.75
WOW buy the barrel off E bay.
http://www.choketube.com/choke-tube-...hoke&x=80&y=10

Just make sure you look over a used ML real good. Buy a bore light and look at that bore. You can also wad up in a small ball some tin foil and use a pen light to look at the bore but isn't as bright as a true bore light.

Al