RCMP tests on a variety of semi-automatic weapons sold in Canada have found the guns can be converted temporarily into fully automatic firearms through an improvised technique described on the internet.

That was the conclusion of an internal report prompted by last year's shooting deaths of three Mounties in Moncton, N.B. The report was delivered to the public safety minister for possible action.

RCMP Commissioner Bob Paulson wrote to Steven Blaney last December, detailing test results on six types of semi-automatics and recommending the government consider laws or regulations to ensure the improvisation technique is prohibited.

Justin Bourque, mug shot

Mountie killer Justin Bourque told RCMP that he had considered making his semi-automatic rifle into a prohibited fully automatic weapon, using an improvised technique. (RCMP)

The Mounties also sent a warning, known as an officer safety alert, to Canadian police forces in January this year tipping them to the technique "so that they may take appropriate enforcement or investigation measures."

"Criminals could … adopt this technique to work around prohibitions on fully automatic firearms, potentially resulting in an increase in gun violence, mass casualties or copycat crimes as the technique is applied more broadly," Paulson advised the minister.

In a response six months later, however, Blaney said changes are not needed.

Law 'sufficiently robust'

"While utilizing such methods to increase the effective rate of fire of semi-automatic firearms is certainly ill-advised, I am of the view that the current legislative framework is sufficiently robust to protect the public from dangerous firing techniques," he wrote on June 29 this year.

CBC News obtained correspondence between Paulson and Blaney on the issue through the Access to Information Act, with significant deletions of sensitive information, including the name and description of the technique tested.

CBC News has independently identified the technique and its presence on the internet, and obtained other documentation, but is withholding details out of concern for public safety.

"We've raised the issue that there's a possible officer safety and public safety issue, and it's for policymakers to decide," Peter Henschel, RCMP deputy commissioner, said in an interview.

'We have demonstrated that there are some weapons that are susceptible to being fired in full automatic mode.' – Peter Henschel, RCMP deputy commissioner

"We have demonstrated that there are some weapons that are susceptible to being fired in full automatic mode."

Henschel declined to provide details, except to say that "mid-range calibre [weapons] based on a military or paramilitary design" are more susceptible to the technique.

Blaney, who retained his Quebec seat in the Oct. 19 election and remains minister until Nov. 4, told CBC News that existing laws and tough sentences are sufficient to deal with potential problems.

"We agree with the RCMP's initial conclusions that this technique does not pose any immediate threat to public safety and that appropriate actions have been taken to address concerns," he said in an email last week.

"Altering a firearm for fully automatic fire is illegal in Canada. Violators could be subject to a lengthy prison sentence of up to 10 years."

The RCMP tests were triggered when Justin Bourque, the 24-year-old Moncton shooter who killed three Mounties and severely injured two, told interrogators he had considered using the technique to upgrade his semi-automatic rifle, a Poly Technologies Model M305 .308-calibre Winchester.

Considered upgrade

Bourque did not carry out the upgrade, but the RCMP, which in 2005 lost four officers at Mayerthorpe, Alta., to a gunman with a semi-automatic rifle, soon ordered the lab work.

"The RCMP has conducted extensive testing of the [blanked out] technique on six firearms, representing a significant spectrum of semi-automatic rifles available on the Canadian market," Paulson told Blaney.

The test report, titled Feasibility and Practicality of Improvised Full Automatic Fire, was entirely withheld in the Access to Information Act package released to CBC News.

Public Safety Minister Stephen Blaney

Public Safety Minister Steven Blaney told the RCMP that existing laws and regulations are sufficient to deal with the possibility that semi-automatic weapons could be turned into more deadly fully automatic firearms. (Adrian Wyld/Canadian Press)

The federal Justice Department looked at the legal framework, and in an April 30 report concluded that "overall, there is ambiguity in the law concerning improvised techniques to convert firearms to automatic fire," says a briefing note for Blaney, dated June 25 this year.

"There are no documented cases where the [blanked out] technique has been used in a criminal offence in Canada. Should this technique be encountered in Canada, law enforcement has the power to act by laying charges under the Criminal Code."

In 2009 and 2013, Canada prohibited models of semi-automatic weapons that had previously been allowed on the market but were later found to be too readily modified to fully automatic status.

But in a third case, Blaney imposed a two-year amnesty after the RCMP determined that CZ 858 and Swiss Arms semi-automatic rifles should also be prohibited because of their susceptibility to conversion to automatics. Blaney's action was widely seen as a rebuke to the Mounties.

The Harper government later passed Bill C-42, which gave the federal cabinet final say in any move to prohibit such weapons.

The newly elected Liberal government's platform promised a series of gun-control measures, but declined to revive the long-gun registry abolished by the Harper government.

"We will take action to get handguns and assault weapons off our streets," says the document, also committing to "repeal changes made by Bill C-42  … [and] put decision-making about weapons restrictions back in the hands of police, not politicians."

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With files from Alison Crawford