By Michael Hirtzer

CHICAGO (Reuters) - A suburban Chicago gun shop said on Thursday it will raffle off a semi-automatic rifle to benefit victims of the Orlando mass shooting despite backlash because the weapon is similar to the one used in the massacre.

The shop, Second Amendment Sports in McHenry, Illinois, has sold more than 100 tickets for $5 each for the July 31 raffle of a Smith & Wesson M&P 15 rifle, which the shop typically sells for $669, co-owner Bert Irslinger Jr said by telephone.

Proceeds from the raffle, in addition to a $2,000 contribution from the store, will benefit the OneOrlando Fund, set up for the victims of the June 12 shooting at the gay nightclub Pulse that killed 49 people in the worst mass shooting in U.S. history.

Gun control groups decried the raffle plan. The Orlando shooter used a Sig Sauer MCX, a semi-automatic rifle like the Smith & Wesson that is being raffled.

"This is like raising money for victims of the Titanic by raffling a cruise. Does Second Amendment Sports have no sense of decency?" Kristen Rand, legislative director of lobbying group Violence Policy Center said in an emailed statement.

The shooting re-ignited a gun control debate in the U.S. Congress, with the House of Representatives announcing on Thursday that it will vote next week on a measure to keep guns out of the hands of people on government terrorism watch lists.

Irslinger, who owns the store with his father Bert Sr, defended the raffle.

"This is not a gun issue; this is a terrorist issue and a hate crime. That's where we're taking a stance," Irslinger Jr said. "There's definitely been backlash. Not in the store, but we've had people call. That's not uncommon in the firearms industry. I just hope they're finding their own way to support."

Irslinger said the shop has previously held raffles to benefit no-kill animal shelters and cancer survivors. "This has been the fastest raffle I've ever sold," he said.

(Editing by Fiona Ortiz and Cynthia Osterman)