FrankSquid has it exactly right. In 1994, I moved into NJ from NY where I had a CCW and a variety of handguns & rifles. Having heard & read the usual NJ stories, I called up the Lt in charge of the Firearms Division of the NJ State Police in Trenton. I asked what I needed to do to dot all the I's & cross all the T's. He said, and I quote "Just bring 'em on in." I couldn't believe it. But he's right. If you've "legally acquire in another jurisdiction", you're good.
NJ Assault weapons: The Colt AR15 is banned by name. Unless yours is quite old, I'll bet it doesn't say "AR15" on the receiver. "Sporter" or "HBAR" or "Match Target" isn't "AR15" and so isn't banned. We have DCM (CMP) matches in several parts of the state and AR's (clones, actually) are everywhere. If you meet the basic federal post-ban requirements, you're ok in NJ. Mags should be blocked to 15 rounds with a piece of wood lathe or some empty shells inside the floorplate to meet the letter of the law. No one has EVER asked me about mag capacity. No cops, not Fed's on the range next to me, not anyone. I'd hate for you to be the first, though, so block 'em.
You will need a FPIC, Firearms Purchaser's Identification Card to buy ammo or long guns. But that's generally no sweat, unless you get a real prick of a Chief of Police in your town.
Check out [url]www.nationalccw.com[/url] and hit the NJ links at the bottom of the page for NJ info. The text of the NJ laws are searchable from a "judiciary" link on [url]www.state.nj.us[/url].
Enjoy, & welcome back to NJ. Join the fight & vote for Schundler for govornor this November.
Norm