Sverre: I haven't used that slug but I use other 200 gn slugs in the 357 revolver. I have used similar slugs in lever action rifles and found that the wider the nose or metplat, and the location of the crimping grooves, the more difficult it may be to find the correct seating depth to assure positive feeding - but thankfully this can be dealt with using taper crimp dies if need be...
If your Marlin chambers the round properly and easily then you are likely set to see how she shoots that slug. I use Winchester 296 with my the 200 gn swcs I prefer. My old Winchester data shows 12.8 gns of 296 for that slug. It has long been accepted that H110 and WW296 are the same powder, so you shold be able to use that load safely. Winchester always recommends a tight crimp to facilitate complete powder burning and I agree. This is an easy shooting load in my revolver and should be the same in your rifle.
This is a gas-checked slug you're thinking of and it should shoot well in the Marlin, even if it is a micro-groove barrel. Beartooth Bullets has completed a phenomenal amount of research using cast and gas checked slugs in micro-groove barrels and the results are almost incredible. take a look at the data they have compiled and if they have done for the 357 what they have done for the 44, 444 and 45, it is information you will want to have on hand. HTH. Mikey.
