Upper assembly order

[Disciple]

With regard to assembling an upper using a barrel nut that does not need indexing. Can the gas block be installed on the barrel before the gas tube is installed in the gas block? It looks like there is room to slide the gas tube deeper into the receiver, index and install the block, then slide the tube out into the gas block and pin it. Will it work?

[Old Bob]

Yup, you can do that. I've replaced gas tubes without removing the gas block.

[redhat]

Yes, that’s how I do it on barrels that come with a front sight block installed. No pint in removing it if you don’t have to.