If I buy a sim free Iphone 6 model A1586 will it work outside of the USA?

What you want is neither. You want an UNLOCKED iPhone 6. You can buy it from Apple online or at a Apple store. SIM-free is different from unlocked. You may not be able to buy the A1586, however, without a contract with Verizon or Sprint. The A1549 is the phone that is sold unlocked and without restriction. It will work anywhere in the world on GSM networks, but may not support LTE everywhere.

I recently bought two different iPhones (a 6 and a 5S). Both for T-Mobile with no contract. I paid full price for them. When I transferred the sim cards from my previous iphones (ATT) and brought them up on the network, the welcome screen said the phone was now unlocked. They continue to work with the ATT network here in the US. Hope this helps.