Hi Snap, and welcome to the Handi gang!
I agree with Datil about it definitely being able to handle the cartridge it was manufactured for.
However, it ain't likely that NEF will add ANY high pressure barrel to the frame. Phone them with the serial number to find out for sure.
I phoned them about a .308 I have, and was told they would not put any higher pressure barrel on... those marked with an asterisk (*) in the barrel accessory flyer, of which the .308 Win is one - even though it came with a .308 Win barrel! It is a 1995 manufacture as well.
The issue seems to be a 'legal' one about which was the original company that manufactured the gun. (post or pre-Marlin)
Doesn't seem to make practical common sense, but the truth is, when issues with legalities enter the picture, one should not remain too attached to practical common sense!
Cheers
Kerr