There is a good article at the firearms blog concerning the tappet system of operation. This is the operating system used on the M-1 Carbine and on the Beretta 30 carbine rifle. Check it out.
http://www.thefirearmblog.com/blog/2014/09/19/short-history-tappet-operation/
While I am on the topic of interesting stuff on the internet. If you have not been to Impro Guns you should check it out. Here is there web page.
http://homemadeguns.wordpress.com/
One last link and that is for a guy that makes some nice stuff. I go to his site quite frequently to study his methods.
http://rifleshooter.com/author/rifl1406/
Thanks for sharing my article! I’m glad you enjoyed it.