“The people who wrote the bill didn’t even know we existed in the state,” said Richard Fitzpatrick, the founder and president of the company, one of the country’s largest producers of magazines and other firearm accessories for gun enthusiasts, law enforcement and the military.

The warning from Erie-based Magpul underscores the political pressures Democrats are weighing as they advance the strictest gun-control measures lawmakers have ever considered in a state that still prides its frontier spirit. Other gun-control proposals include universal background checks, a ban on concealed firearms on campuses, and holding assault-weapon sellers and owners liable for shootings.

Opponents need only three Democrats in the Senate to vote no against the magazine proposal to defeat it, and two have already said they won’t support the bill. But most Democrats are not budging.