The New York City Department of Correction is shelling out about $150,000 for ammunition and assorted firearms accessories — marking its third major purchase of guns or gun-related products in the last 12 months.

The newest buy includes nearly $64,000 for spotting scopes and tripods, about $20,000 for rifle scopes and more than $69,000 for ammunition, records show.

The new gear, first reported by Gothamist on Sunday, will add to the veritable arsenal the DOC has assembled over the last year – which includes 10 sniper rifles bought last November and 30 submachine guns picked up in June.

A department spokesperson justified the purchases Monday by saying its members serve as first responders and can be called on to respond to critical incidents throughout the city – including any reports of a potential gunman at LaGuardia Airport.

“DOC’s Emergency Services Unit officers are … the first unit mobilized to assist the Port Authority with active shooter situations, due to Rikers’ proximity to LaGuardia,” the spokesperson said.

“The new guns will replace existing older models of the same [or] substantially-similar long arms in the DOC arsenal.”

A DOC source also insisted the purchase was necessary to keep city jails – such as on the troubled Rikers Island – safe.

“Common sense says that there dangerous people in the care and custody of Department of Correction and it needs to be a secure location” the source told The Post.

Not everyone thinks the big-ticket buys are a good idea, however – especially when the cash-strapped city is looking to cut budgets across the board.

Marc Bullaro, a former assistant deputy warden at Rikers, told Gothamist that it’s not likely correction officers will actually use the equipment.

“We’re talking about El Chapo,” Bullaro told the outlet, referring to imprisoned Mexican drug lord Joaquín Guzmán as an example of when guards might pull out their new toys.

“We’re not talking about the average guy in New York City who kills somebody or who gets arrested for five kilos of cocaine.”

Bullaro also said the department should use the cash it’s spending on guns and ammo for other things.

“If DOC didn’t have these guns, you still have the police department, the state police, and all these other agencies that have these weapons,” he told the outlet. “This money should be going for other stuff.”

Last November, the DOC dropped $100,000 for 10 sniper rifles – just as it grappled with security issues at the oft-troubled Rikers Island complex.

The weapons – long-range M-10 rifles from the Rochester-based Amchar Wholesale Inc. – were issued to a specially trained team for “extraordinary, high-risk situations,” a DOC spokesman said at the time.

Some didn’t like that purchase either, and wondered why the island jail complex needed such high-powered weaponry.

“It’s not like anybody will be storming Rikers Island – and if they did, I’m pretty sure they have enough ammunition to combat that,” one law enforcement source told The Post at the time.

“I would say save weapons like that for the NYPD, the ATF, drug enforcement.”

But the department continued to build its cache, picking up 30 Heckler & Koch MP5s for more than $90,00 in June – all the while saying these, too, would only be used by a specially-trained team facing extraordinary, high-risk situations.

Keith Taylor, a 23-year veteran of the NYPD Emergency Services Unit and a former DOC assistant correction commissioner, said at the time that the MP5s were a vital part of the jail’s arsenal and not “for in-house stuff.”

“If they are doing tactical security operations such as escorting high-valued target prisoners to and from court proceedings, they have to have a plan in place that would include having the use of sufficient weaponry to deal with any kind of threats that they may need,” said Taylor, who is now an adjunct professor at the John Jay College of Criminal Justice in Manhattan.

“They can’t rely on the NYPD to handle all their security issues, so they have to have that capability themselves,” he added.

Those guns came from Thomas J. Morris III/Eagle Point Gun in Thorofare, a licensed New Jersey gun dealer that contracts with the city.

The gun buys come as the DOC continues to face a withering storm of criticism over complaints about harsh conditions at Rikers and their failure to report inmate deaths as legally required.

Earlier this year, the DOC sparked more backlash when it announced that it will no longer announce when an inmate dies behind bars.

The change in policy came after DOC officials reportedly tried to quell a federal monitor’s report about five disturbing incidents behind bars over a six-day period in May.

The monitor was installed in 2015 to address claims that guards regularly used unnecessary force.

In April, City Hall agreed to pay more than $53 million to settle class-action claims that some inmates were mistreated, confined in tight spaces and deprived of sunlight while behind bars.

The settlement — which was the culmination of a lawsuit brought by a dozen men who claimed they were beaten by Rikers Island guards — also instituted a number of other reforms, such as strict rules against guards striking inmates on the head, a body camera mandate and the installation of 8,000 security cameras throughout the complex.