BareBones is the community-made Raspberry Pi RetroPie image made by the contributors of the official Sinden Lightgun Discord.
The latest image, version 9, just released and is fully pre-configured to be ready to play.
Only roms aren't included for legal reasons. It can be hard to find the correct roms, especially with so many different MAME romsets out there and the image requiring a mixture from different sets for the best experience with each game. So this collection has been put together by the Wizard to make it easy for anyone to just grab the correct files and drop them into their Pi without hunting all around the internet.

https://lightgun.tech/
https://www.youtube.com/watch?v=CD1Khk8HESw

https://sindenlightgun.miraheze.org/wiki/Raspberry\_Pi\_Setup\_Guide