Shot Peening

I have an on-going project in the works right now involving the AR series rifles and carbines. This site is proving invaluable in my research.

The various threads in this section are especially useful to me and I appreciate the expertise available here.

Right now I am researching Shot Peening, the manufacturing step that has again and again popped up as one of the must have steps in the manufacture of the BCG.

I have found a number of excellent resources on the net on the subject, including this video on YouTube that explain the process and usefulness of the step in relation to manufacturing in general. It is also pretty clear from these sources why one would want the BCG shot peened.

What I would like is to hear from those who build carbines rifles what the specific advantages are to the firearms world? Are there hardening methods that produce beneficial results in place of shot peening (not necessarily superior, but functional in it's own right) that is cheaper, and thus desirable by some manufactures? If so, what are the differences?

Lastly, can a machine component, such as the BCG parts, be shot peened after the fact to improve quality of the piece?

I would like to thank those that answer and apologize if this has been asked and I missed in my forum searches. Also, I do understand to a small extent working metals, but only soft metals such as copper and nickel, so some technical language is fine.

Here's a good primer on shot peening:
http://www.metalimprovement.com/shot_peening.php

Thank you, Sir.

Bump, does anyone have anything to add?