20 ga. Barrel for Navy Arms .58 cal. Buffalo Hunter?

[Hawkdancer]

I have an early model .58 cal Buffalo Hunter rifle and I understand there is a drop in 20 ga. Barrel to convert the stock and lock to a shotgun.  The challenge is I have not been able to find any information on the barrel.  Any help would be appreciated.  Thanks,
Hawkdancer

[Eric Krewson]

I did an extensive web search and only found an old Gunbroker and where a similar rifle had sold with both rifled and smoothbore barrels. The seller said the smoothbore barrels were sold in stated that didn't allow rifles for deer hunting.