One thing I've learned about the various new shot types is that "rules of thumb" are usually unreliable and you should only work to laboratory (pressure gun) tested data. I presume ecotungsten will be no different. That's especially the case if you've got an old Parker with short chambers. The loads I've suggested are for 3,1/2" shells with nitro powders in my Remington SP10 but Ballistic Products or Precision Reloading are still likely to be the place to go to for components. Some of my hulls are cut down for a neighbour who has a British made 3,1/4" double 10 bore.
