Thankfully, in the end, he wasn't able to use the weapon, nor any of the others he wanted to buy to wage a war.
That's because the Dundalk republican was caught red handed trying to buy guns and explosives for the Real IRA, the organisation behind the Omagh bombing.
It was a sting involving MI5 and Lithuanian authorities that led to his demise; and it lasted four years.
Operation Uncritical began in 2004.
Contact was first made when the Real IRA decided they wanted to buy explosives and weapons from Eastern Europe.
So Campbell and others placed their trust in a man they thought could deliver the goods.
He turned out to be an undercover agent.
However, he wasn't the only part of a team Campbell mistakenly thought was on his side.
Relations cooled for a while but the arms deal was back on track late in 2006.
And the Real IRA had quite a shopping list.
Rocket launchers, sniper rifles, hand-grenades and semtex explosives.
Of course money had to change hands and the weapons had to be tested.
A lot of travel was involved, from England to Ireland, Poland to Spain and eventually Lithuania.
First negotiations took place in a dingy lock-up.
The merchandise was inspected, then it was tested under the blue skies of the Lithuanian countryside.
Here's the chilling conversation Campbell had with an associate about what they'd planned to do with explosives.
That was to bomb England.
Campbell: "You imagine us getting over to England if you'd ten of them and ten clocks in a holdall. You imagine, with a six hour timer we could be over to London and back.
Associate: "Two or three"
Campbell "Just tick tick tick tick...gone. Leave it anywhere."
But it wasn't just England in their sights - Northern Ireland too.
In a Lithuanian lock-up, Campbell had a conversation with the agent posing as the arms dealer.
Campbell: "We will be shooting from across borders. The border."
Agent: "Okay"
Campbell: "You know, that's the position we will be in."
Agent: "And who will be target?"
Campbell: "Brits".
In another meeting in the same lock-up, this time with two agents, Campbell is pressed again on what he wants to do with the weapons - and who he represents.
Campbell: "For enemies."
Agent 1: "Enemies?"
Campbell: Enemies.
Agent 1: "Enemies. So you...who are you?
Campbell: " Who am I?
Agent 1: "Yeah"
Campbell: "Who am I?"
Agent 1: "Yeah"
Campbell: "My organisation?"
Agent 1: "I need....I don't need your organisation, but I have to know who are you."
Campbell: "You have to know my name? No no..."
Agent 2: "Tell, tell, tell, him er, sorry guys..tell, tell, tell him organisation don't...tell him your organisation don't tell your name."
Campbell: "Tell him the name of the organisation?"
Agent 2: "Yeah, yeah, yeah."
Campbell: "IRA"
Agent 1: "What?"
Campbell: "IRA"...
Michael Campbell had his suspicions that the bogus arms dealer may have been an agent.
He was even interroragated, bundled into the back of a van and taken to South Armagh.
But the agent, who now has a new identity and new life, held his resolve - as did the other.
Operation Uncritical was, in fact, one of the most significant stings carried out by the security services and was a major blow for dissident republican terrorists.
Since, there have been killings and bomb attacks; But the authorities believe that putting Campbell behind bars, and stopping his attempts to bolster the Real IRA's armoury, did save lives.