Sorry to muddy up the water. Just sayin' don't be afraid to buy a LoneStar if you can get a good deal on it. I would not order one if your'e in a hurry. It took nearly 6 months to get mine. You can get a 2500X tomorrow from Killough's (although at 2X the price of a LoneStar). Is the 2500X twice as good? I don't know. But Killough's is a lot quicker at making them, and they are top quality as evidenced by its widespread and successful use.
Bill Calfee's book, The Art of Rimfire Accuracy has a review of over 10 actions that you might be able to find on the used market and points out the pros and cons of each action. They include The Remington 40X, XP-100, Model 54 Anschutz, Winchester 52, Suhl 150, 2007/2013 Anschutz, Time, ULA, 37 Remington, Turbo, Hall and Kelby. Sadly the 2500X, Trident and LoneStar came after Calfee's review. Although most of the discussion and comments about the Remington 40X and XP-100 cover the LoneStar, with the LoneStar's re-design by Stiller fixing many of the issues.
BTW, Calfee's pick of all the actions he reviewed was the Turbo, specifically the Turbo V3. I see Turbo's for sale from time to time. You can still order a new one I believe, but I think the lead times are long and they are the same price as a 2500X or Trident.
Good luck with your search.