If it is expanding at less than 1000 fps, it will probably not also penetrate much (given practical .429" bullet masses). I believe sufficient penetration is more critical than expansion and would not be willing to trade the former for the latter unless low penetration was suitable for my target. There may be a few bullets that are carefully designed to expand in a limited way so they maintain sectional density for penetration. The Hornady XTP is likely the only one that is available in .429". Hornady, Federal and Winchester (Olin) have some other bullet designs for .45 that carefully strike a balance of penetration and expansion, like Critical Duty or Ranger T Series. If you can get Remington Golden Sabers in .429", I would try those and see if the results are accetable. I don't shoot .429, but I get good expansion with GS in another caliber at low velocities. The penetration is marginal but acceptable.
