The weapon was purchased from a Facebook advertisement.
Concerns are being raised over the ease with which a gun could be bought online.
A journalist responded to an advertisement on Facebook Ireland for the device , and it was delivered to an office in Dublin.
Meta's taken down the advertisement and says such adverts are in breach of its policies.
The gun was immediately handed over to Gardai and investigations are ongoing.
Security Analyst and Mullingar's Declan Power says there are serious implications regarding the ability to buy weapons or imitation guns online:
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