Firearms Development Corp action. Called POFF
10 inches long by 1.7 in diameter with extended bolt handle and machined lug. tenon is 1 and 3/16 in diameter, so use a 1.350 barrel for plenty of shoulder tapered to whatever.
338 Lapua Bolt face. The action is big enough for sure for the 408, but would require mods to work if the bolt face has enough metal. Probably too much work for the 408, would be my guess, but welcome to try.
This is a BR chrome moly action for big calibers. Often used in the LR rigs for 378s etc. Extremely smooth action.
Was saving this for a 338 build but ran across a deal so this one is for sale.
PICs are below. Click on them to enlarge.
There is a smaller version for sale on BR central that is selling for $1100, Only difference is mine is larger and not plated.
Benchrest Central Classifieds - Components
$750 and shipping to your ffl.