[brucelee]

How is it done?

 

[Jeremy]

It almost has to be done by a pro.

The barrel will need headspaced and I have never seen a new M1a barrel that is finished. they come "short chambered" so a 'smith can chamber and fit it to your reciever.

There are so many different receivers that are made just a hair different but it's a big difference when it comes to barreling.

 

[Adler]

have to have a smith do it. Requires headspacing the chamber and finishing it. Plus getting the gas block and port lined up. Its not usually a cheap deal like on an AK or AR.