Setting Headspace on an AR ?

[hylander]

I want to put my own Upper together using a DPMS SS DCM Fluted barrel.
They say it comes fully Chambered with Barrel Extention installed, but not head spaced.
Planning on using an RRA Upper & BCG.
So how do I set Head Space on an AR ?

[bjl333]

If you are assembling from brand new parts then the chances of it being off are very slim. Get a go/no go gauge from Midway or Brownells.

[oldyeller]

If the barrel extension is installed properly, the head space should be fine. There is no way to adjust the head space once the extension is installed and pinned.