Understand the way the retail system is set up.

In the case of barrels I would suggest you look at places like egun. I just happened to run into a sale at www.egun.de in Germany, where a .458 Lott M03 Africa barrel (new) was offered for only 750 Euros. A lot of people here are selling /swapping M03 barrels at discounted prices because they are moving up or down caliber groups or are in a position similar to yours, where they bought the M03, but wanted to swap the barrel later on. EGUN caters only to Germans, but there should be something similar in the US. At any rate, African calibers can be had here cheaply, basically new, because many people who bought them don't like the recoil after all

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Other option: You seem not like the caliber you currently have. Was just at a German gun forum which was discussing the merits of the M03. Mauser Germany appears to exchange (new and like) barrels without charge - maybe Mauser USA does as well.