Transaction declined: Charge declined RESTRICTED CARD Customer bank does not allow this card to be used at this type of merchant.” 

Gun rights advocates warned that a new change to the credit card industry to add a firearm and ammunition-specific Merchant Category Code (MCC) for gun stores wasn’t about tracking guns necessarily, but could lead to the denial of lawful firearms purchases by law-abiding citizens.

In September, Visa, Mastercard, and American Express all said they would adopt the MCC code to categorize sales at gun shops; months later, several social media posts of alleged gun stores and customers claim they experienced card issues.

https://www.zerohedge.com/political/gun-shops-and-customers-claim-credit-card-firms-restrict-purchases