Legendary void machine gun?

[MULTIPASS]

Is there no way to get one outside of a raid or unavailable seasonal content? I know there's a new exotic in Lightfall, kind of feels like they were aware of the gap and plugged it in the most recent paid content...

[Kylito]

Corrective Measure, the Vault Of Glass machine gun, is the main F2P void one. Retrofit Escapade and Shattered Cipher are both void MGs that are from old seasonal content, so it's possible for them to be available at Xur/Banshee.
I heavily recommend getting gear for and trying to do Vault, as it is a very easy and simple raid that is quite noob-friendly, and is farmable on certain weeks. If you REALLY don't want to do raids, then just check Xur/Banshee every week.

[Nakos]

Retrofit Escapade is literally from last season. Most people probably already have one.

Both Retrofit Escapade and Shattered Cipher are in Xûr's loot pool. Watch him when he shows up, eventually he'll have one or the other.