Looked at the long barrel more closely, not a standard .32. Barrel diameter is .278 mm land-to-land.
Assuming you meant .278" it sounds like you may have one of them thar Savage Nambu's.
Mine has a standard .32 magazine with it currently.
The OAL of a 7mm Nambu round appears too long for the standard magazine.
This one can accommodate 1 round only and bumps the front of the magazine using a 7mm snap cap.
The snap cap was made from a .30 carbine case that doesn't dimension perfectly.
Original 7mm Nambu ammo is extremely difficult to find and if you do is ~$50-75 per round.
