The Senate is set for a final vote Thursday on a Liberal gun-control bill that has been one of the government’s most contentious pieces of legislation since Public Safety Minister Ralph Goodale tabled it in the Commons more than a year ago.

Conservative senators were still engaged Tuesday in a last-minute attempt to amend the bill after successfully gutting it with support from a non-affiliated senator in the Senate’s national security and defence committee.

Senators in the Independent Senators Group, most of whom have supported the bill throughout its passage in the Upper Chamber, were expected to vote down a Conservative amendment attempt on Tuesday.

But though the Senate minority Conservatives were thought to be planning to move other amendments, iPolitics has learned the government leader in the Senate and other caucus leaders have already agreed on a third-reading vote Thursday.

“They might try more amendments, but the leaders have an agreement third-reading will be voted Thursday,” an Independent Senator told iPolitics.

The legislation could receive Royal Assent later that day, with Parliament set to adjourn for a scheduled May recess next week.

The bill was the Liberal government’s first try at fulfilling a 2015 election promise for stiffer control over firearms, with a separate initiative last fall, led by Border Security and Organized Crime Reduction Minister Bill Blair, to take action against handgun crimes and the kind of assault weapons used in mass shootings.

Conservative MPs and senators, and vocal leaders of firearm rights groups and their lobbyists, have fought Bill C-71 tooth and nail because it focuses on reinstating controls over the sale of non-restricted rifles and shotguns, including mandatory records by retailers and a requirement to confirm the validity of gun licences with the RCMP before a sale goes through.

Sport shooters and the associations many of them belong to also oppose a reinstatement of requirements for individual transportation permits each time an owner of restricted handguns or rifles wants to take their weapons to a gunsmith, gun show or border point, with a valid licence being the only requirement to transport restricted firearms to a licensed shooting range.

The Conservatives passed an array of amendments to the bill in committee, with support from New Brunswick non-affiliated Senator David Richards and indirect support from P.E.I. Sen. Diane Griffin, who either abstained in votes or voted with the Conservatives.

Although the Independent senator who chaired the committee, former Ontario Provincial Police commissioner Gwen Boniface, voted against many of the amendments, tied motions in Senate committees fail.

When the majority of ISG senators voted to reject the committee report, including the amendments, the Senate process automatically reverted to a vote on the original bill as it was when the Senate sent it to committee. The overwhelming majority of Independent senators, supported by a small remaining band of Independent Liberals, voted to send the original bill into third-reading debate.

The bill includes a major change to background checks for gun licence applicants and licence renewals. Rather than a five-year screening for violence or self-harm by the buyer or owner renewing a licence, the checks will go back through the lifetime of an applicant or even a gun owner who is renewing a five-year licence.

Firearm organizations and the Conservatives claim a reinstated specific requirement for production of a valid licence at point of sale, to be confirmed by a call to the RCMP and recorded without detail on the gun being bought, is similar to the maintenance of a long-gun registry the former Conservative government dismantled in 2012.

Opponents also claim a requirement for retailers to keep detailed records of gun sales and the buyer’s licence number, to be available through court approval in a police investigation, is also a form of registry that the Liberal party had promised not to introduce.

The bill also proposes to reverse amendments to the Criminal Code that allowed the Conservative cabinet to overrule an RCMP re-classification of specific makes of semi-automatic rifles that had been imported to Canada from Czechoslovakia and Switzerland. Cabinet reversed the RCMP classification shortly before the 2015 federal election.

The RCMP had re-classified the rifles to prohibited status from restricted or unrestricted on evidence the rifles had been converted from automatic military rifles into semi-automatic rifles, and could easily be converted back to automatic.

Bill C-71 reverts to Criminal Code wording that allows Cabinet only to re-classify semi-automatic rifles to a higher level of restriction from a lower one.

Gun owners who hold the weapons to be reclassified as prohibited rifles will be able to keep them through a grandfathering clause, but will have to store them and keep them under existing controls for prohibited firearms.