A rifle? No. A handgun? Yes, either permit to purchase or CCW.
No you don't to own. But to purchase you do.
There is no registration to own firearms in Iowa. A form 4473 is required to purchase firearms in the US, but those are kept by the gunshop. Rifles and shotguns require a NICS check performed by the gunshop. The NICS check can take up to 3 days for approval. Handguns require either a permit to purchase or a permit to carry. It is essentually a NICS check performed by your county sheriff's office. The permit gets you preapproval for purchase of any firearm so it is faster than the NICS check. Permits are good for 5 years and can be used to acquire multiple firearms during that time. You can still posess your handguns when your permit expires, but you cannot carry it and transport requires special care. Primarily, it must be cased, unloaded and out of reach of the driver and other occupants of the vehicle. I am not sure how citizenship enters into the system with you coming from Australia. You did not say whether you are a US citizen.
You do not need a gun license to purchase or own a long gun. However you DO to purchase a handgun.
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