Since Sig P320 is a modular gun which can be converted to other calibers using the same serialized frame, would it be NJ legal?

IMO, yes. The serialized part is the gun. It's a little different from purely caliber conversion kits as you can change the grips, the slides... but the principle is still the same; you still use the same serialized part.

It's no different from having a lower receiver and adding all kinds of uppers and accessories to it.

2 minutes ago, WP22 said:

IMO, yes. The serialized part is the gun. It's a little different from purely caliber conversion kits as you can change the grips, the slides... but the principle is still the same; you still use the same serialized part.

It's no different from having a lower receiver and adding all kinds of uppers and accessories to it.

Thanks! This is logical and what I thought but who knows with NJ nonsense laws they in their ultimate wisdom didn't differentiate between rifles and pistols ...