No it won't. Its designed for an external thread.
Vepr barrel is much thicker.
870 barrel at the muzzle is already thin from the choke, so unless you are shooting a cylinder barrel with no chokes (aka slugs and 00 buckshot only) I wouldn't externally thread the barrel.
There are 870 specific brakes or ported chokes for the existing internal choke thread you can get if you do want a door breaching tacticool/zombie armageddon 12 gauge.
http://www.brownells.com/shotgun-par...prod72174.aspx
http://www.brownells.com/shotgun-par...0Outside%20USA
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