The photograph of a 3D print out shotgun was posted on Telegram, a social media network, accompanied by the words: "The day is coming…when reasonable men must do unreasonable things.
"That time is fast approaching."
In the comments section one person has replied, "That time has already passed," while another adds: "I’ve been waiting over a year for the call."
However, the most sinister reply states: "Only two bullets there, one for the leak (Mr Varadkar) one for mehole (Minister Martin) what about Ryan and Donnelley (sic).
One person replies: "That’s only the two shells you can see."
A Government spokesperson said they would not comment on issues regarding security measures.
The Proud Boys have previously had a social media presence in Ireland and have actively recruited members in other countries outside the US.
In the US, they are one of a number of far-right groups who have been linked to the use of 3D printers to build homemade guns.
Using printers and machining tools, a number of US groups have built their own homemade weapons – ones that can shoot very real, and very deadly bullets.
The neo-fascist Proud Boys are notorious in the US where they played a key role in the attack on the Capitol on January 6.
A Federal indictment issued after the attack presented fresh evidence of how officials believe members planned and carried out a coordinated attempt to stop Congress certifying Joe Biden’s electoral victory over Donald Trump.
At least 19 leaders, members or associates of the Proud Boys have been charged in federal court with offenses related to the 6 January riot.
“We need to start planning and we are starting planning for a Biden presidency,” one alleged leader wrote after the Capitol invasion, according to the indictment.
On 6 January, the Proud Boys marched to the Capitol before Trump finished addressing thousands of supporters near the White House.
About two hours later, just before Congress convened a joint session to certify the election results, a group of Proud Boys followed a crowd who breached barriers at a pedestrian entrance to the Capitol grounds, the indictment says.
Several Proud Boys entered the Capitol after the mob smashed windows and forced open doors.
A Wall Street Journal investigation of video footage found Proud Boys members were “key instigators”, at the “forefront” in many pivotal moments.
The messages in the indictment show the Proud Boys using military language before and during the attack, one asking if leaders should hold a “commander’s briefing” before gathering at the Washington Monument.
The assistant US attorney Jason McCullough had described the day’s events as “an incredible attack on our institutions of government.”