This is generally not allowed in most gun stores. The concern is whether this classifies as a “straw purchase” per ATF rules, which are designed to prevent persons from purchasing guns for those that cannot legally possess them.
For example: A convicted felon wants to purchase a gun, so he has his friend fill out the paperwork while he “helpfully pays” for his “friend’s” gun.
Since gun stores are not private investigators, the blanket policy is not to allow any transaction that could potentially be a straw purchase in disguise.
However, since the ATF realizes there are legitimate reasons a person might wish to help pay for another person’s firearm (i.e. an uncle helping pay for his niece’s first handgun) they have offered an alternative: At the gun store owner’s discretion, a customer may purchase a gift card and give it to the person who is buying the gun.
At Guns Etc, we do allow gift-card purchases in these types of situations. However, the person who is buying the gun MUST be the person who fills out the ATF paperwork and submits to the FBI background check.
See this article from the National Shooting Sports Foundation for more information: https://www.nssf.org/articles/giving-a-firearm-as-a-gift-some-reminders-from-nssf/
As an additional note: If any employee of any gun store suspects that the intended purpose of the gift card purchase (or purchase in general) is to give the gun to a prohibited-possessor, they have the right to refuse the sale.