It is the 1640 action. It is either a model 4000 or 4100 depending on whether it is a standard or monte carlo stock, but that doesn't much matter. The 1640 action is what is important. Huber is the only one that makes a trigger kit for the rifle that doesn't require modification of the stock. I have one but have not fitted it to the rifle. If you do a google search, I believe there was someone that reviewed the Huber Concepts trigger here on the campfire. There are also some old triggers produced by Timney that were marketed/sold by Tradewinds that are pretty hard to find.
