The brake is a great feature. Screw off and put a thread-protector cap on the muzzle, ad lib.
Iron sights ? As old as I am, I would rather have a QD scope with backup scope or red dot in my kit ready to go. To each his own, your mileage may vary, etc.
If it is a simple neck-down of the 404 Jeffery case to .416 bullet:
A .416 Dakota reamer will clean it up and handloading dies for that are available from Redding.
I glued on a .416 Dakota and a .423 Dakota to this souvenir cartridge board that I picked up on a visit to Dakota Arms in Sturgis, SD, bought my Redding .416 Dakota and .423 Dakota dies on that visit too, about 20 years ago.
That was not long before then-new CEO upstart Charlie Kokesh bankrupted the old company.
The .423 Lapua might have been the last hurrah, his pet cartridge.
Ironically the .423 Dakota was a "404" done on a shortened .416 Rigby-.338 Lapua Magnum case, close enough.
I would hope for a straight-forward .416/404 Jeffery that is easy to re-chamber to .416 Dakota, use same brass as 404 Jeffery, fire-formed, or find properly head-stamped brass made by Norma at one time.
Or enjoy the prestige of the unadulterated .416/404 Jeffery Unimproved, reloaded as 6.5 wildcatter says.
When Dakota Arms insisted on requiring me to buy a walnut stocked M76 if I wanted them to do a synthetic stock for my rifle, this po'boy took matters into his own Gunsmith's hand.
Barrel stamping is not prissy at all: 416 DAKOTA