Cash helps, as regards electronic payment records, but if an FFL transfer is involved, it’s the paperwork that is the issue, not the payment.
Face to face private sales can be safer, but some sellers insist on keeping a record, including buyer’s ID, “to protect themselves” from possible overzealous government agents.
I know such s privatr sellrr.
Firearm owners who brag of their items make themselves targets for the liebrrals.
Actually bragging about anything one possesses can leade to bad things happening.