The Ulti mag uses chokes that are a different diameter than the regular mossy chokes. The 835 is overbored so it uses different chokes. If you want to use aftermarket chokes always..always ..go with Briley. They probably make the best chokes for about every application you can find. Unless you are going to do an awful lot of steel shot shooting go for the regular Briley chokes. For steel..get the factory chokes. They are much cheaper and will probably do most everything you are ever going to need. Now the next thing you do...go shoot. Don't listen to Dom..you don't need 2 bbls. Most shooting can be done with an improved cylinder choke. Get a light mod too. Those 2 will take care of 90% of all the shooting you will ever do. You know how those elitist snobs in Germany are

They'll have ya shooting a Drilling or Vierling if they can convince you to.

Which reminds me...i almost bought a Drilling the other day. nice gun but pretty old