From the article:
The language of federal gun laws restricts ownership to people who are unable to manage their own affairs
due to "marked subnormal intelligence, or mental illness, incompetency, condition, or disease” – which could potentially affect a large group within Social Security, the LA Times reported.
If Social Security, which has never taken part in the background check system, uses the same standard as the Department of Veterans Affairs – which is the idea floated – then
millions of beneficiaries could be affected, with about 4.2 million adults receiving monthly benefits that are managed by “representative payees.”
It would not affect those who's affairs are managed by another UNLESS they are declared mentally incompetent and it would take a court to do that.
Meme claims Obama to ban Social Security recipients from owning guns
This is a vast exaggeration of the actual policy under consideration. It would not affect all Social Security recipients, but rather
those who have already been declared mentally incompetent, and thus ineligible under current law from purchasing a gun. And it is targeted at blocking gun purchases, not taking away guns from people who already have them. Only in California could the policy lead to increased gun seizures, and only -- potentially -- for mentally incompetent residents of the state who would be newly added to the background check database.