So, if you want a genuine Russian Moisin Nagant, Saiga, VEPR, Nagant revolver or whatever, you might want to buy now. In the case of Moisin Nagant's with WWII optics, and AKM variants in particular, it is most likely that these weapons will double in value shortly after, or even before, sanctions are announced.
Be careful, however, to remember that unless you have an applicable federal license, you cannot legally engage in the business of buying and selling firearms. So, don't run out and buy a dozen Saiga-12s. You probably could make a tidy profit reselling them, but in an ironic twist of fate, you, as a common US citizen, are prohibited by federal law from capitalizing on your knowledge of Russo-American arms trade and cannot personally benefit in any deliberate way from the likely market changes so clearly on the horizon ... unless, I suppose, you can identify a publicly traded corporation that is likely to benefit greatly from those changes (and I can't think of a single one off hand).
What's worse is that this kind of road into economic sanctions is likely to work to Putin's favor, giving him a clearer external enemy to focus the Russian citizenry upon. If I had to bet a paycheck on it, I'd say Putin probably planned to trigger US trade sanctions all along.