Re: Ideas for .338 lapua mag build?
I don't know anything about the 338 Lapua that is inexpensive. I currently shoot a 277 cal wildcat based on the 338 Lapua case and am also in the process of building another wildcat that will be a 338 Lapua Improved variant.
To develop the full potential of the cartridge, your seating depth will be such that you will not be able to have a repeating rifle w/o going with one of the longer CIP magazines which require modifications to both the std. LA actions, stocks and bottom metal. The Lapua case head is larger than the std. magnum case head requiring a special bolt (which in turn may require special modifications to the action.
My first Lapua was built on a std. Rem 700 Mag LA. The bolt face had to be opened, leaving precious little metal surrounding the case head itself. back then, there were few alternatives, so this was the solution. Today, there are other alternatives, and most gunsmiths won't even entertain the notion of opening & using a std. mag bolt face for reasons of safety and liability. Maybe you can find one....
The magazine in the std. Rem magnum configuration is just a tad too short to feed loaded 338 Lapua cases, especially when using the longer 300 gr. bullets. You can purchase aftermarket bottom metal and longer magazines, but nearly all require modifying the bolt stop to increase the throw of the bolt, along with the removal of some metal from the lower part of the action and recutting / re-inletting the stock for the new bottom metal. The cheaper way around this (and the one my rifle has) is to simply glue the follower to the bottom of the action, which effectively makes it a single shot. I have never found this arrangement to be a hinderance, as most LR shots take time to set up anyway.
My current build sidesteps these issues. I have a Stiller TAC-338 action on order. The platform is a McRee's Gen-5 folder with CIP magazine. Neither of which I would describe as inexpensive.
I believe your best route to do an inexpensive build is to buy a used/donor Rem 700 or Savage LA Mag action and then replace the bolt and go with different bottom metal. The other big 338's, such as the 338 EDGE and 338 RUM have the same head case measurements as your std. magnums and cycle well in std. length actions. These two cartridges are inexpensive to build as usually no modification to the bolt or bottom metal are required. The 338 Norma Mag has the diameter head as the Lapua, but it is shorter and will also cycle in std. length magnum actions. I'm sure others will chime in as well with what they have experienced. Good Luck.